Index: Makefile.inc1
===================================================================
--- Makefile.inc1
+++ Makefile.inc1
@@ -128,10 +128,25 @@
 TARGET_ABI=	gnueabi
 .endif
 .endif
-MACHINE_ABI?=	unknown
-MACHINE_TRIPLE?=${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${MACHINE_ABI}-freebsd13.0
-TARGET_ABI?=	unknown
-TARGET_TRIPLE?=	${TARGET_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${TARGET_ABI}-freebsd13.0
+MACHINE_VENDOR?=	unknown
+TARGET_VENDOR?=		unknown
+
+# The triple has the general format <arch><sub>-<vendor>-<sys>-<abi>
+# See https://clang.llvm.org/docs/CrossCompilation.html#target-triple
+.ifndef MACHINE_TRIPLE
+MACHINE_TRIPLE?=${MACHINE_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${MACHINE_VENDOR}-freebsd${OS_VERSION}
+.ifdef MACHINE_ABI
+MACHINE_TRIPLE:=${MACHINE_TRIPLE}-${MACHINE_ABI}
+.endif
+.endif
+
+.ifndef TARGET_TRIPLE
+TARGET_TRIPLE?=	${TARGET_ARCH:S/amd64/x86_64/:C/hf$//:S/mipsn32/mips64/}-${TARGET_VENDOR}-freebsd${OS_VERSION}
+.ifdef TARGET_ABI
+TARGET_TRIPLE:=${TARGET_TRIPLE}-${TARGET_ABI}
+.endif
+.endif
+
 KNOWN_ARCHES?=	aarch64/arm64 \
 		amd64 \
 		arm \
Index: Makefile.libcompat
===================================================================
--- Makefile.libcompat
+++ Makefile.libcompat
@@ -17,7 +17,7 @@
 .if ${WANT_COMPILER_TYPE} == gcc || \
     (defined(X_COMPILER_TYPE) && ${X_COMPILER_TYPE} == gcc)
 .else
-LIB32CPUFLAGS+=	-target x86_64-unknown-freebsd13.0
+LIB32CPUFLAGS+=	-target x86_64-unknown-freebsd${OS_VERSION}
 .endif
 LIB32CPUFLAGS+=	-m32
 LIB32WMAKEENV=	MACHINE=i386 MACHINE_ARCH=i386 \
@@ -49,9 +49,9 @@
 .endif
 .else
 .if ${TARGET_ARCH:Mmips64el*} != ""
-LIB32CPUFLAGS=  -target mipsel-unknown-freebsd13.0
+LIB32CPUFLAGS=  -target mipsel-unknown-freebsd${OS_VERSION}
 .else
-LIB32CPUFLAGS=  -target mips-unknown-freebsd13.0
+LIB32CPUFLAGS=  -target mips-unknown-freebsd${OS_VERSION}
 .endif
 .endif
 LIB32CPUFLAGS+= -mabi=32
Index: lib/clang/llvm.build.mk
===================================================================
--- lib/clang/llvm.build.mk
+++ lib/clang/llvm.build.mk
@@ -10,6 +10,10 @@
 .error Please define SRCDIR before including this file
 .endif
 
+.ifndef OS_VERSION
+.error Please define OS_VERSION before including this file
+.endif
+
 .PATH:		${LLVM_SRCS}/${SRCDIR}
 
 CFLAGS+=	-I${SRCTOP}/lib/clang/include
@@ -29,14 +33,16 @@
 TARGET_ABI=	-gnueabihf
 .elif ${TARGET_ARCH:Marm*}
 TARGET_ABI=	-gnueabi
+.elif defined(TARGET_ABI)
+TARGET_ABI:=	-${TARGET_ABI}
 .else
 TARGET_ABI=
 .endif
+
 VENDOR=		unknown
-OS_VERSION=	freebsd13.0
 
-LLVM_TARGET_TRIPLE?=	${TARGET_ARCH:C/amd64/x86_64/:C/arm64/aarch64/}-${VENDOR}-${OS_VERSION}${TARGET_ABI}
-LLVM_BUILD_TRIPLE?=	${BUILD_ARCH:C/amd64/x86_64/:C/arm64/aarch64/}-${VENDOR}-${OS_VERSION}
+LLVM_TARGET_TRIPLE?=	${TARGET_ARCH:C/amd64/x86_64/:C/arm64/aarch64/}-${VENDOR}-freebsd${OS_VERSION}${TARGET_ABI}
+LLVM_BUILD_TRIPLE?=	${BUILD_ARCH:C/amd64/x86_64/:C/arm64/aarch64/}-${VENDOR}-freebsd${OS_VERSION}
 
 CFLAGS+=	-DLLVM_DEFAULT_TARGET_TRIPLE=\"${LLVM_TARGET_TRIPLE}\"
 CFLAGS+=	-DLLVM_HOST_TRIPLE=\"${LLVM_BUILD_TRIPLE}\"
Index: share/mk/sys.mk
===================================================================
--- share/mk/sys.mk
+++ share/mk/sys.mk
@@ -346,3 +346,10 @@
 .endif
 
 .endif # ! Posix
+
+# Parse FreeBSD version from /sys/sys/param.h and creates OS_VERSION
+# in the format used by clang's '-target' parameter (i.e. 13.0, 13.10)
+OS_VERSION!=grep '\#define __FreeBSD_version' $${SRCTOP}/sys/sys/param.h |\
+	awk '{ major=int(substr($$3,1,length($$3)-5)); \
+		minor=int(substr($$3,length($$3)-4,2)); \
+		print major "." minor }'