Index: Mk/bsd.gcc.mk
===================================================================
--- Mk/bsd.gcc.mk
+++ Mk/bsd.gcc.mk
@@ -17,6 +17,15 @@
 # do so by specifying USE_GCC=X+ which requests at least GCC version X.
 # To request a specific version omit the trailing + sign.
 #
+# Optional comma-separated arguments may be specified after the version
+# specifier. The following arguments are supported:
+#   build ... Add GCC as a build dependency (BUILD_DEPENDS).
+# If no arguments are specified, GCC is added both as a build dependency
+# and a runtime dependency.
+#
+# USE_GCC=build is a shortcut for USE_GCC=yes:build.
+#
+#
 # Examples:
 #   USE_GCC=	yes			# port requires a current version of GCC
 #							# as defined in bsd.default-versions.mk.
@@ -23,6 +32,9 @@
 #   USE_GCC=	any			# port requires GCC 4.2 or later.
 #   USE_GCC=	7+			# port requires GCC 7 or later.
 #   USE_GCC=	5			# port requires GCC 5.
+#   USE_GCC=    8:build     # port requires GCC 8 at build-time only.
+#   USE_GCC=    build		# port requires a current version of GCC at
+#							# build-time only.
 #
 # If you are wondering what your port exactly does, use "make test-gcc"
 # to see some debugging.
@@ -49,6 +61,35 @@
 # No configurable parts below this. ####################################
 #
 
+# Alias USE_GCC=build to USE_GCC=yes:build
+.if ${USE_GCC} == build
+USE_GCC:=		yes:${USE_GCC}
+.endif
+
+# Split arguments
+.if defined(USE_GCC)
+__USE_GCC:=		${USE_GCC:C/\:.*//}
+_USE_GCC_ARGS:=	${USE_GCC:C/^[^\:]*(\:|\$)//:S/,/ /g}
+USE_GCC=		${__USE_GCC}
+.endif
+
+.if ${_USE_GCC_ARGS:Mbuild}
+_USE_GCC_BUILD_DEP=	yes
+_USE_GCC_ARGS:=		${_USE_GCC_ARGS:Nbuild}
+.endif
+
+.if !empty(_USE_GCC_ARGS)
+IGNORE=	Bad target specification in USE_GCC; only "build" is supported
+.endif
+
+# If the port does not specify a specific dependency, assume all are required.
+.if !defined(_USE_GCC_BUILD_DEP) && !defined(_USE_GCC_RUN_DEP)
+_USE_GCC_BUILD_DEP:=     yes
+_USE_GCC_RUN_DEP:=       yes
+.endif
+
+
+# Handle USE_GCC=yes.
 .if defined(USE_GCC) && ${USE_GCC} == yes
 USE_GCC=	${GCC_DEFAULT}+
 .endif
@@ -177,8 +218,12 @@
 CXXFLAGS:=		${CXXFLAGS:N-mretpoline}
 
 .if defined(_GCC_PORT_DEPENDS)
+. if defined(_USE_GCC_BUILD_DEP)
 BUILD_DEPENDS+=	${_GCC_PORT_DEPENDS}:lang/${_GCC_PORT}
+. endif
+. if defined(_USE_GCC_RUN_DEP)
 RUN_DEPENDS+=	${_GCC_PORT_DEPENDS}:lang/${_GCC_PORT}
+. endif
 # Later GCC ports already depend on binutils; make sure whatever we
 # build leverages this as well.
 USE_BINUTILS=	yes