Index: head/gnu/usr.bin/gdb/Makefile.inc
===================================================================
--- head/gnu/usr.bin/gdb/Makefile.inc	(revision 359773)
+++ head/gnu/usr.bin/gdb/Makefile.inc	(revision 359774)
@@ -1,71 +1,71 @@
 # $FreeBSD$
 
 .include <src.opts.mk>
 
 VERSION= "6.1.1 [FreeBSD]"
 VENDOR= marcel
 
 PACKAGE=	gdb
 
 BMAKE_GDB= ${.CURDIR:H}
 BMAKE_ROOT= ${BMAKE_GDB:H}
 BMAKE_BU= ${BMAKE_ROOT}/binutils
 
 CNTRB_BU= ${SRCTOP}/contrib/binutils
 CNTRB_GDB= ${SRCTOP}/contrib/gdb
 
 OBJ_BU= ${OBJTOP}/gnu/usr.bin/binutils
 OBJ_GDB= ${OBJTOP}/gnu/usr.bin/gdb
 
 # These assignments duplicate much of the functionality of
 # MACHINE_CPUARCH, but there's no easy way to export make functions...
 
 .if defined(TARGET_ARCH)
 TARGET_CPUARCH=${TARGET_ARCH:${__TO_CPUARCH}}
 .else
 TARGET_CPUARCH=${MACHINE_CPUARCH}
 .endif
 TARGET_ARCH?=	${MACHINE_ARCH}
 TARGET_SUBDIR= ${BMAKE_GDB}/arch/${TARGET_CPUARCH}
 
 .if ${TARGET_ARCH} != ${MACHINE_ARCH}
 GDB_CROSS_DEBUGGER=
 .endif
 
 .PATH:	${CNTRB_GDB}/gdb ${CNTRB_GDB}/gdb/cli ${CNTRB_GDB}/gdb/mi	\
 	${CNTRB_GDB}/gdb/signals ${CNTRB_GDB}/gdb/tui ${TARGET_SUBDIR}
 
 CFLAGS+= -DHAVE_CONFIG_H -DRL_NO_COMPAT -DMI_OUT=1
 CFLAGS+= -DDEBUGDIR=\"${DEBUGDIR}\"
 CFLAGS+= -I.
 CFLAGS+= -I${TARGET_SUBDIR}
 CFLAGS+= -I${BMAKE_BU}/libbfd -I${BMAKE_BU}/libbfd/${TARGET_CPUARCH}
 CFLAGS+= -I${CNTRB_GDB}/gdb
 CFLAGS+= -I${CNTRB_GDB}/gdb/config
 CFLAGS+= -I${CNTRB_BU}/include
 CFLAGS+= -I${CNTRB_GDB}/include
 CFLAGS+= -I${CNTRB_BU}/bfd
 CFLAGS+= -I${SYSROOT:U${DESTDIR}}/${INCLUDEDIR}/edit
 
 # Some bits here currently rely on some of the linker-merging magic that happens
 # with -fcommon.  While this is the default right now, explicitly set -fcommon
 # so that it continues to build when the default flips.
-CFLAGS+= -fcommon
+CFCOMMONFLAG= -fcommon
 
 GENSRCS+= nm.h tm.h
 
 .if defined(GDB_CROSS_DEBUGGER)
 CFLAGS+= -DCROSS_DEBUGGER -I${BMAKE_ROOT:H:H}
 GDB_SUFFIX= -${TARGET_ARCH}
 MAN=
 .else
 BINDIR?=	/usr/libexec
 MAN=
 .endif
 
 .include "${TARGET_SUBDIR}/Makefile"
 
 SRCS+= ${GENSRCS}
 CLEANFILES+= ${GENSRCS}
 
 .include "../Makefile.inc"
Index: head/share/mk/src.sys.mk
===================================================================
--- head/share/mk/src.sys.mk	(revision 359773)
+++ head/share/mk/src.sys.mk	(revision 359774)
@@ -1,44 +1,45 @@
 # $FreeBSD$
 
 # Note: This file is also duplicated in the sys/conf/kern.pre.mk so
 # it will always grab SRCCONF, even if it isn't being built in-tree
 # to preserve historical (and useful) behavior. Changes here need to
 # be reflected there so SRCCONF isn't included multiple times.
 
 .if !defined(_WITHOUT_SRCCONF)
 # Allow user to configure things that only effect src tree builds.
 SRCCONF?=	/etc/src.conf
 .if !empty(SRCCONF) && \
     (exists(${SRCCONF}) || ${SRCCONF} != "/etc/src.conf") && \
     !target(_srcconf_included_)
 
 # Validate that the user didn't try setting an env-only variable in
 # their src.conf. This benefits from already including bsd.mkopt.mk.
 .for var in ${__ENV_ONLY_OPTIONS:O:u}
 __presrcconf_${var}:=	${MK_${var}:U-}${WITHOUT_${var}:Uno:Dyes}${WITH_${var}:Uno:Dyes}
 .endfor
 
 .sinclude "${SRCCONF}"
 _srcconf_included_:	.NOTMAIN
 
 # Validate the env-only variables.
 .for var in ${__ENV_ONLY_OPTIONS:O:u}
 __postrcconf_${var}:=	${MK_${var}:U-}${WITHOUT_${var}:Uno:Dyes}${WITH_${var}:Uno:Dyes}
 .if ${__presrcconf_${var}} != ${__postrcconf_${var}}
 .error Option ${var} may only be defined in ${SRC_ENV_CONF}, environment, or make argument, not ${SRCCONF}.
 .endif
 .undef __presrcconf_${var}
 .undef __postrcconf_${var}
 .endfor
 
 .endif # SRCCONF
 .endif
 
 # The following should be removed no earlier than LLVM11 being imported into the
 # tree, to ensure we don't regress the build.  LLVM11 and GCC10 will switch the
 # default over to -fno-common, making this redundant.
-CFLAGS+=	-fno-common
+CFCOMMONFLAG?=	-fno-common
+CFLAGS+=	${CFCOMMONFLAG}
 
 # tempting, but bsd.compiler.mk causes problems this early
 # probably need to remove dependence on bsd.own.mk 
 #.include "src.opts.mk"