Makefile.inc1: Enable requesting the universe toolchain.

make universe builds a cross toolchain under HOST_OBJTMP/tmp via the
universe-toolchain target.  However, doing a plain 'make buildworld'
after a universe/tinderbox run (e.g. to reproduce a failure and test
the fix for it), will try to build a new cross toolchain under
OBJTMP/tmp which can be tedious.  This commit adds a make variable
(UNIVERSE_TOOLCHAIN) which can be used similar to CROSS_TOOLCHAIN to
request an external toolchain.  If this variable is set (value doesn't
matter), the the universe toolchain is used as an external toolchain.

Reviewed by:	imp
Differential Revision:	https://reviews.freebsd.org/D40777

Makefile.inc1

@@ -73,6 +73,12 @@ TIME_ENV ?= time env
 .error CROSS_TOOLCHAIN ${CROSS_TOOLCHAIN} not found
 .endif
 CROSSENV+=CROSS_TOOLCHAIN="${CROSS_TOOLCHAIN}"
+.elif defined(UNIVERSE_TOOLCHAIN)
+UNIVERSE_TOOLCHAIN_PATH?=${HOST_OBJTOP}/tmp/usr/bin
+XCC?="${UNIVERSE_TOOLCHAIN_PATH}/cc"
+XCXX?="${UNIVERSE_TOOLCHAIN_PATH}/c++"
+XCPP?="${UNIVERSE_TOOLCHAIN_PATH}/cpp"
+XLD?="${UNIVERSE_TOOLCHAIN_PATH}/ld"
 .endif
 .if defined(CROSS_TOOLCHAIN_PREFIX)
 CROSS_COMPILER_PREFIX?=${CROSS_TOOLCHAIN_PREFIX}
@@ -718,6 +724,7 @@ BMAKEENV=	INSTALL="sh ${.CURDIR}/tools/install.sh" \
 BSARGS= 	DESTDIR= \
 		OBJTOP='${WORLDTMP}/obj-tools' \
 		OBJROOT='$${OBJTOP}/' \
+		UNIVERSE_TOOLCHAIN_PATH=${UNIVERSE_TOOLCHAIN_PATH} \
 		MAKEOBJDIRPREFIX= \
 		BOOTSTRAPPING=${BOOTSTRAPPING_OSRELDATE} \
 		BWPHASE=${.TARGET:C,^_,,} \
@@ -789,6 +796,7 @@ KTMAKE=		${TIME_ENV} \
 		DESTDIR= \
 		OBJTOP='${WORLDTMP}/obj-kernel-tools' \
 		OBJROOT='$${OBJTOP}/' \
+		UNIVERSE_TOOLCHAIN_PATH=${UNIVERSE_TOOLCHAIN_PATH} \
 		MAKEOBJDIRPREFIX= \
 		BOOTSTRAPPING=${BOOTSTRAPPING_OSRELDATE} \
 		-DNO_CPU_CFLAGS \

Makefile.libcompat

@@ -37,6 +37,7 @@ LIB${_LIBCOMPAT}WMAKE+=	${TIME_ENV} ${LIB${_LIBCOMPAT}WMAKEENV} ${MAKE} \
 			${LIB${_LIBCOMPAT}WMAKEFLAGS} \
 			OBJTOP=${LIB${_LIBCOMPAT}_OBJTOP} \
 			OBJROOT='$${OBJTOP}/' \
+			UNIVERSE_TOOLCHAIN_PATH=${UNIVERSE_TOOLCHAIN_PATH} \
 			MAKEOBJDIRPREFIX= \
 			MK_INCLUDES=no \
 			MK_MAN=no MK_HTML=no