When building world with clang, for gnu/lib/libobjc, sys/boot/i386/boot2

and sys/boot/pc98/boot2, do not simply assign 'gcc' to CC, since compile
flags are sometimes passed via this variable, for example during the
build32 stage on amd64.  This caused the 32-bit libobjc build on amd64
to fail.

Instead, only replace the first instance of clang (if any, including
optional path) with gcc, and leave the arguments alone.

Approved-by:	rpaulo (mentor)

gnu/lib/libobjc/Makefile

@@ -16,9 +16,7 @@ SRCS=	archive.c class.c encoding.c gc.c hash.c init.c linking.m misc.c \
 	selector.c sendmsg.c thr.c thr-objc.c exception.c
 
 # XXX: clang cannot compile libobjc yet
-.if ${CC:T:Mclang} == "clang"
-CC=gcc
-.endif
+CC:=${CC:C/^(.*\/)?clang$/gcc/1}
 
 INCS=	encoding.h hash.h objc-api.h objc-decls.h objc-list.h objc.h runtime.h \
 	sarray.h thr.h typedstream.h NXConstStr.h Object.h Protocol.h

sys/boot/i386/boot2/Makefile

@@ -3,9 +3,7 @@
 .include <bsd.own.mk>
 
 # XXX: clang can compile the boot code just fine, but boot2 gets too big
-.if ${CC:T:Mclang} == "clang"
-CC=gcc
-.endif
+CC:=${CC:C/^(.*\/)?clang$/gcc/1}
 
 FILES=		boot boot1 boot2
 

sys/boot/pc98/boot2/Makefile

@@ -3,9 +3,7 @@
 .include <bsd.own.mk>
 
 # XXX: clang can compile the boot code just fine, but boot2 gets too big
-.if ${CC:T:Mclang} == "clang"
-CC=gcc
-.endif
+CC:=${CC:C/^(.*\/)?clang$/gcc/1}
 
 FILES=		boot boot1 boot2