Index: head/Makefile
===================================================================
--- head/Makefile
+++ head/Makefile
@@ -143,7 +143,7 @@
 	stage-packages \
 	create-packages-world create-packages-kernel create-packages \
 	packages installconfig real-packages sign-packages package-pkg \
-	print-dir test-system-compiler
+	print-dir test-system-compiler test-system-linker
 
 # These targets require a TARGET and TARGET_ARCH be defined.
 XTGTS=	native-xtools native-xtools-install xdev xdev-build xdev-install \
@@ -168,7 +168,7 @@
 	_* build32 buildfiles buildincludes buildkernel buildsoft \
 	buildworld everything kernel-toolchain kernel-toolchains kernel \
 	kernels libraries native-xtools showconfig test-system-compiler \
-	tinderbox toolchain \
+	test-system-linker tinderbox toolchain \
 	toolchains universe world worlds xdev xdev-build
 
 .ORDER: buildworld installworld
Index: head/Makefile.inc1
===================================================================
--- head/Makefile.inc1
+++ head/Makefile.inc1
@@ -97,9 +97,74 @@
 # Pull in COMPILER_TYPE and COMPILER_FREEBSD_VERSION early. Pull it from the
 # tree to be friendlier to foreign OS builds. It's safe to do so unconditionally
 # here since we will always have the right make, unlike in src/Makefile
+# Don't include bsd.linker.mk yet until XBINUTILS is handled (after src.opts.mk)
+_NO_INCLUDE_LINKERMK=	t
 .include "share/mk/bsd.compiler.mk"
+.undef _NO_INCLUDE_LINKERMK
+# src.opts.mk depends on COMPILER_FEATURES
 .include "share/mk/src.opts.mk"
 
+.if ${TARGET} == ${MACHINE}
+TARGET_CPUTYPE?=${CPUTYPE}
+.else
+TARGET_CPUTYPE?=
+.endif
+.if !empty(TARGET_CPUTYPE)
+_TARGET_CPUTYPE=${TARGET_CPUTYPE}
+.else
+_TARGET_CPUTYPE=dummy
+.endif
+.if ${TARGET} == "arm"
+.if ${TARGET_ARCH:Marmv[67]*} != "" && ${TARGET_CPUTYPE:M*soft*} == ""
+TARGET_ABI=	gnueabihf
+.else
+TARGET_ABI=	gnueabi
+.endif
+.endif
+MACHINE_ABI?=	unknown
+MACHINE_TRIPLE?=${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${MACHINE_ABI}-freebsd12.0
+TARGET_ABI?=	unknown
+TARGET_TRIPLE?=	${TARGET_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${TARGET_ABI}-freebsd12.0
+
+# Handle external binutils.
+.if defined(CROSS_TOOLCHAIN_PREFIX)
+CROSS_BINUTILS_PREFIX?=${CROSS_TOOLCHAIN_PREFIX}
+.endif
+# If we do not have a bootstrap binutils (because the in-tree one does not
+# support the target architecture), provide a default cross-binutils prefix.
+# This allows riscv64 builds, for example, to automatically use the
+# riscv64-binutils port or package.
+.if !make(showconfig)
+.if !empty(BROKEN_OPTIONS:MBINUTILS_BOOTSTRAP) && \
+    ${MK_LLD_BOOTSTRAP} == "no" && \
+    !defined(CROSS_BINUTILS_PREFIX)
+CROSS_BINUTILS_PREFIX=/usr/local/${TARGET_TRIPLE}/bin/
+.if !exists(${CROSS_BINUTILS_PREFIX})
+.error In-tree binutils does not support the ${TARGET_ARCH} architecture. Install the ${TARGET_ARCH}-binutils port or package or set CROSS_BINUTILS_PREFIX.
+.endif
+.endif
+.endif
+XBINUTILS=	AS AR LD NM OBJCOPY RANLIB SIZE STRINGS
+.for BINUTIL in ${XBINUTILS}
+.if defined(CROSS_BINUTILS_PREFIX) && \
+    exists(${CROSS_BINUTILS_PREFIX}/${${BINUTIL}})
+X${BINUTIL}?=	${CROSS_BINUTILS_PREFIX:C,/*$,,}/${${BINUTIL}}
+.else
+X${BINUTIL}?=	${${BINUTIL}}
+.endif
+.endfor
+
+# If a full path to an external linker is given, don't build lld.
+.if ${XLD:M/*}
+MK_LLD_BOOTSTRAP=	no
+.endif
+
+.include "share/mk/bsd.linker.mk"
+
+# Begin WITH_SYSTEM_COMPILER / WITH_SYSTEM_LD
+
+# WITH_SYSTEM_COMPILER - Pull in needed values and make a decision.
+
 # Check if there is a local compiler that can satisfy as an external compiler.
 # Which compiler is expected to be used?
 .if ${MK_CLANG_BOOTSTRAP} == "yes"
@@ -109,6 +174,7 @@
 .else
 WANT_COMPILER_TYPE=
 .endif
+
 .if !defined(WANT_COMPILER_FREEBSD_VERSION)
 .if ${WANT_COMPILER_TYPE} == "clang"
 WANT_COMPILER_FREEBSD_VERSION_FILE= lib/clang/freebsd_cc_version.h
@@ -131,6 +197,7 @@
 .endif
 .export WANT_COMPILER_FREEBSD_VERSION WANT_COMPILER_VERSION
 .endif	# !defined(WANT_COMPILER_FREEBSD_VERSION)
+
 # It needs to be the same revision as we would build for the bootstrap.
 # If the expected vs CC is different then we can't skip.
 # GCC cannot be used for cross-arch yet.  For clang we pass -target later if
@@ -147,7 +214,52 @@
 MK_GCC_BOOTSTRAP=	no
 USING_SYSTEM_COMPILER=	yes
 .endif	# ${WANT_COMPILER_TYPE} == ${COMPILER_TYPE}
+
+# WITH_SYSTEM_LD - Pull in needed values and make a decision.
+
+# Check if there is a local linker that can satisfy as an external linker.
+# Which linker is expected to be used?
+.if ${MK_LLD_BOOTSTRAP} == "yes"
+WANT_LINKER_TYPE=		lld
+.elif ${MK_BINUTILS_BOOTSTRAP} == "yes"
+# Note that there's no support for bfd in WITH_SYSTEM_LINKER.
+WANT_LINKER_TYPE=	bfd
+.else
+WANT_LINKER_TYPE=
+.endif
+
+.if !defined(WANT_LINKER_FREEBSD_VERSION)
+.if ${WANT_LINKER_TYPE} == "lld"
+WANT_LINKER_FREEBSD_VERSION_FILE= lib/clang/include/lld/Common/Version.inc
+WANT_LINKER_FREEBSD_VERSION!= \
+	awk '$$2 == "LLD_REVISION_STRING" {gsub(/"/, "", $$3); print $$3}' \
+	${SRCDIR}/${WANT_LINKER_FREEBSD_VERSION_FILE} || echo unknown
+WANT_LINKER_VERSION_FILE= lib/clang/include/lld/Common/Version.inc
+WANT_LINKER_VERSION!= \
+	awk '$$2 == "LLD_VERSION" {split($$3, a, "."); print a[1] * 10000 + a[2] * 100 + a[3]}' \
+	${SRCDIR}/${WANT_LINKER_VERSION_FILE} || echo unknown
+.else
+WANT_LINKER_FREEBSD_VERSION_FILE=
+WANT_LINKER_FREEBSD_VERSION=
+.endif
+.export WANT_LINKER_FREEBSD_VERSION WANT_LINKER_VERSION
+.endif	# !defined(WANT_LINKER_FREEBSD_VERSION)
+
+.if ${MK_SYSTEM_LINKER} == "yes" && \
+    (${MK_LLD_BOOTSTRAP} == "yes") && \
+    !make(showconfig) && !make(xdev*) && \
+    ${X_LINKER_TYPE} == ${WANT_LINKER_TYPE} && \
+    ${X_LINKER_VERSION} == ${WANT_LINKER_VERSION} && \
+    ${X_LINKER_FREEBSD_VERSION} == ${WANT_LINKER_FREEBSD_VERSION}
+# Everything matches, disable the bootstrap linker.
+MK_LLD_BOOTSTRAP=	no
+USING_SYSTEM_LINKER=	yes
+.endif	# ${WANT_LINKER_TYPE} == ${LINKER_TYPE}
+
+# WITH_SYSTEM_COMPILER / WITH_SYSTEM_LINKER - Handle defaults and debug.
 USING_SYSTEM_COMPILER?=	no
+USING_SYSTEM_LINKER?=	no
+
 TEST_SYSTEM_COMPILER_VARS= \
 	USING_SYSTEM_COMPILER MK_SYSTEM_COMPILER \
 	MK_CROSS_COMPILER MK_CLANG_BOOTSTRAP MK_GCC_BOOTSTRAP \
@@ -155,20 +267,40 @@
 	WANT_COMPILER_FREEBSD_VERSION WANT_COMPILER_FREEBSD_VERSION_FILE \
 	CC COMPILER_TYPE COMPILER_FEATURES COMPILER_VERSION \
 	COMPILER_FREEBSD_VERSION \
-	X_COMPILER_TYPE X_COMPILER_FEATURES X_COMPILER_VERSION \
-	X_COMPILER_FREEBSD_VERSION \
-	LINKER_TYPE LINKER_FEATURES LINKER_VERSION \
-	X_LINKER_TYPE X_LINKER_FEATURES X_LINKER_VERSION
-test-system-compiler: .PHONY
-.for v in ${TEST_SYSTEM_COMPILER_VARS}
+	XCC X_COMPILER_TYPE X_COMPILER_FEATURES X_COMPILER_VERSION \
+	X_COMPILER_FREEBSD_VERSION
+TEST_SYSTEM_LINKER_VARS= \
+	USING_SYSTEM_LINKER MK_SYSTEM_LINKER \
+	MK_LLD_BOOTSTRAP MK_BINUTILS_BOOTSTRAP \
+	WANT_LINKER_TYPE WANT_LINKER_VERSION WANT_LINKER_VERSION_FILE \
+	WANT_LINKER_FREEBSD_VERSION WANT_LINKER_FREEBSD_VERSION_FILE \
+	LD LINKER_TYPE LINKER_FEATURES LINKER_VERSION \
+	LINKER_FREEBSD_VERSION \
+	XLD X_LINKER_TYPE X_LINKER_FEATURES X_LINKER_VERSION \
+	X_LINKER_FREEBSD_VERSION
+
+.for _t in compiler linker
+test-system-${_t}: .PHONY
+.for v in ${TEST_SYSTEM_${_t:tu}_VARS}
 	${_+_}@printf "%-35s= %s\n" "${v}" "${${v}}"
 .endfor
-.if ${USING_SYSTEM_COMPILER} == "yes" && \
-    (make(buildworld) || make(buildkernel) || make(kernel-toolchain) || \
+.endfor
+.if (make(buildworld) || make(buildkernel) || make(kernel-toolchain) || \
     make(toolchain) || make(_cross-tools))
+.if ${USING_SYSTEM_COMPILER} == "yes"
 .info SYSTEM_COMPILER: Determined that CC=${CC} matches the source tree.  Not bootstrapping a cross-compiler.
+.elif ${MK_CLANG_BOOTSTRAP} == "yes"
+.info SYSTEM_COMPILER: libclang will be built for bootstrapping a cross-compiler.
 .endif
+.if ${USING_SYSTEM_LINKER} == "yes"
+.info SYSTEM_LINKER: Determined that LD=${LD} matches the source tree.  Not bootstrapping a cross-linker.
+.elif ${MK_LLD_BOOTSTRAP} == "yes"
+.info SYSTEM_LINKER: libclang will be built for bootstrapping a cross-linker.
+.endif
+.endif
 
+# End WITH_SYSTEM_COMPILER / WITH_SYSTEM_LD
+
 # Store some compiler metadata for use in installworld where we don't
 # want to invoke CC at all.
 _COMPILER_METADATA_VARS=	COMPILER_VERSION \
@@ -177,7 +309,8 @@
 				COMPILER_FREEBSD_VERSION \
 				LINKER_VERSION \
 				LINKER_FEATURES \
-				LINKER_TYPE
+				LINKER_TYPE \
+				LINKER_FREEBSD_VERSION
 compiler-metadata.mk: .PHONY .META
 	@: > ${.TARGET}
 	@echo ".info Using cached compiler metadata from build at $$(hostname) on $$(date)" \
@@ -190,61 +323,7 @@
 	@echo ".export ${_COMPILER_METADATA_VARS}" >> ${.TARGET}
 	@echo ".export ${_COMPILER_METADATA_VARS:C,^,X_,}" >> ${.TARGET}
 
-.if ${TARGET} == ${MACHINE}
-TARGET_CPUTYPE?=${CPUTYPE}
-.else
-TARGET_CPUTYPE?=
-.endif
-.if !empty(TARGET_CPUTYPE)
-_TARGET_CPUTYPE=${TARGET_CPUTYPE}
-.else
-_TARGET_CPUTYPE=dummy
-.endif
-.if ${TARGET} == "arm"
-.if ${TARGET_ARCH:Marmv[67]*} != "" && ${TARGET_CPUTYPE:M*soft*} == ""
-TARGET_ABI=	gnueabihf
-.else
-TARGET_ABI=	gnueabi
-.endif
-.endif
-MACHINE_ABI?=	unknown
-MACHINE_TRIPLE?=${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${MACHINE_ABI}-freebsd12.0
-TARGET_ABI?=	unknown
-TARGET_TRIPLE?=	${TARGET_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${TARGET_ABI}-freebsd12.0
 
-# Handle external binutils.
-.if defined(CROSS_TOOLCHAIN_PREFIX)
-CROSS_BINUTILS_PREFIX?=${CROSS_TOOLCHAIN_PREFIX}
-.endif
-# If we do not have a bootstrap binutils (because the in-tree one does not
-# support the target architecture), provide a default cross-binutils prefix.
-# This allows riscv64 builds, for example, to automatically use the
-# riscv64-binutils port or package.
-.if !make(showconfig)
-.if !empty(BROKEN_OPTIONS:MBINUTILS_BOOTSTRAP) && \
-    ${MK_LLD_BOOTSTRAP} == "no" && \
-    !defined(CROSS_BINUTILS_PREFIX)
-CROSS_BINUTILS_PREFIX=/usr/local/${TARGET_TRIPLE}/bin/
-.if !exists(${CROSS_BINUTILS_PREFIX})
-.error In-tree binutils does not support the ${TARGET_ARCH} architecture. Install the ${TARGET_ARCH}-binutils port or package or set CROSS_BINUTILS_PREFIX.
-.endif
-.endif
-.endif
-XBINUTILS=	AS AR LD NM OBJCOPY RANLIB SIZE STRINGS
-.for BINUTIL in ${XBINUTILS}
-.if defined(CROSS_BINUTILS_PREFIX) && \
-    exists(${CROSS_BINUTILS_PREFIX}/${${BINUTIL}})
-X${BINUTIL}?=	${CROSS_BINUTILS_PREFIX:C,/*$,,}/${${BINUTIL}}
-.else
-X${BINUTIL}?=	${${BINUTIL}}
-.endif
-.endfor
-
-# If a full path to an external linker is given, don't build lld.
-.if ${XLD:M/*}
-MK_LLD_BOOTSTRAP=	no
-.endif
-
 # We must do lib/ and libexec/ before bin/ in case of a mid-install error to
 # keep the users system reasonably usable.  For static->dynamic root upgrades,
 # we don't want to install a dynamic binary without rtld and the needed
@@ -857,6 +936,9 @@
 	fi
 .endfor
 .endif	# ${USING_SYSTEM_COMPILER} == "yes"
+.if ${USING_SYSTEM_LINKER} == "yes"
+	@rm -f ${WORLDTMP}/usr/bin/ld ${WORLDTMP}/usr/bin/ld.lld
+.endif	# ${USING_SYSTEM_LINKER} == "yes"
 .endif	# !defined(NO_CLEAN)
 	@mkdir -p ${WORLDTMP}
 	@touch ${WORLDTMP}/${.TARGET}
Index: head/share/mk/bsd.compiler.mk
===================================================================
--- head/share/mk/bsd.compiler.mk
+++ head/share/mk/bsd.compiler.mk
@@ -208,5 +208,7 @@
 .endif	# ${cc} == "CC" || !empty(XCC)
 .endfor	# .for cc in CC XCC
 
+.if !defined(_NO_INCLUDE_LINKERMK)
 .include <bsd.linker.mk>
+.endif
 .endif	# !target(__<bsd.compiler.mk>__)
Index: head/share/mk/bsd.linker.mk
===================================================================
--- head/share/mk/bsd.linker.mk
+++ head/share/mk/bsd.linker.mk
@@ -16,6 +16,8 @@
 # - retpoline: support for generating PLT with retpoline speculative
 #              execution vulnerability mitigation
 #
+# LINKER_FREEBSD_VERSION is the linker's internal source version.
+#
 # These variables with an X_ prefix will also be provided if XLD is set.
 #
 # This file may be included multiple times, but only has effect the first time.
@@ -29,7 +31,8 @@
 # Try to import LINKER_TYPE and LINKER_VERSION from parent make.
 # The value is only used/exported for the same environment that impacts
 # LD and LINKER_* settings here.
-_exported_vars=	${X_}LINKER_TYPE ${X_}LINKER_VERSION ${X_}LINKER_FEATURES
+_exported_vars=	${X_}LINKER_TYPE ${X_}LINKER_VERSION ${X_}LINKER_FEATURES \
+		${X_}LINKER_FREEBSD_VERSION
 ${X_}_ld_hash=	${${ld}}${MACHINE}${PATH}
 ${X_}_ld_hash:=	${${X_}_ld_hash:hash}
 # Only import if none of the vars are set somehow else.
@@ -55,10 +58,14 @@
 .endif
 .if ${_ld_version:[1..2]} == "GNU ld"
 ${X_}LINKER_TYPE=	bfd
+${X_}LINKER_FREEBSD_VERSION=	0
 _v=	${_ld_version:M[1-9].[0-9]*:[1]}
 .elif ${_ld_version:[1]} == "LLD"
 ${X_}LINKER_TYPE=	lld
 _v=	${_ld_version:[2]}
+${X_}LINKER_FREEBSD_VERSION!= \
+	${${ld}} --version | \
+	awk '$$3 ~ /FreeBSD/ {print substr($$4, 1, length($$4)-1)}'
 .else
 .warning Unknown linker from ${ld}=${${ld}}: ${_ld_version}, defaulting to bfd
 ${X_}LINKER_TYPE=	bfd
@@ -85,6 +92,7 @@
 X_LINKER_TYPE=		${LINKER_TYPE}
 X_LINKER_VERSION=	${LINKER_VERSION}
 X_LINKER_FEATURES=	${LINKER_FEATURES}
+X_LINKER_FREEBSD_VERSION= ${LINKER_FREEBSD_VERSION}
 .endif	# ${ld} == "LD" || (${ld} == "XLD" && ${XLD} != ${LD})
 
 # Export the values so sub-makes don't have to look them up again, using the
Index: head/share/mk/src.opts.mk
===================================================================
--- head/share/mk/src.opts.mk
+++ head/share/mk/src.opts.mk
@@ -168,6 +168,7 @@
     SVNLITE \
     SYSCONS \
     SYSTEM_COMPILER \
+    SYSTEM_LINKER \
     TALK \
     TCP_WRAPPERS \
     TCSH \
Index: head/tools/build/options/WITHOUT_SYSTEM_LINKER
===================================================================
--- head/tools/build/options/WITHOUT_SYSTEM_LINKER
+++ head/tools/build/options/WITHOUT_SYSTEM_LINKER
@@ -0,0 +1,16 @@
+.\" $FreeBSD$
+Set to not opportunistically skip building a cross-linker during the
+bootstrap phase of the build.
+Normally, if the currently installed linker matches the planned bootstrap
+linker type and revision, then it will not be built.
+This does not prevent a linker from being built for installation though,
+only for building one for the build itself.
+The
+.Va WITHOUT_LLD
+and
+.Va WITHOUT_BINUTILS
+options control those.
+.Pp
+This option is only relevant when
+.Va WITH_LLD_BOOTSTRAP
+is set.
Index: head/tools/build/options/WITH_SYSTEM_LINKER
===================================================================
--- head/tools/build/options/WITH_SYSTEM_LINKER
+++ head/tools/build/options/WITH_SYSTEM_LINKER
@@ -0,0 +1,16 @@
+.\" $FreeBSD$
+Set to opportunistically skip building a cross-linker during the
+bootstrap phase of the build.
+If the currently installed linker matches the planned bootstrap linker
+type and revision, then it will not be built.
+This does not prevent a linker from being built for installation though,
+only for building one for the build itself.
+The
+.Va WITHOUT_LLD
+and
+.Va WITHOUT_BINUTILS
+options control those.
+.Pp
+This option is only relevant when
+.Va WITH_LLD_BOOTSTRAP
+is set.