Revert "config.mak.uname: use clang for Mac OS X 10.6"

This reverts commit 7b6daf8.

Now that st_add4() has been patched to work around the gcc 4.2.x
compiler crash, revert the sledge-hammer approach of forcing Mac OS X
10.6 to unconditionally use 'clang' rather than the default compiler
(gcc).

Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.mak.uname

@@ -102,9 +102,6 @@ ifeq ($(uname_S),Darwin)
 	ifeq ($(shell expr "$(uname_R)" : '[15]\.'),2)
 		NO_STRLCPY = YesPlease
 	endif
-	ifeq ($(shell test "`expr "$(uname_R)" : '\([0-9][0-9]*\)\.'`" -eq 10 && echo 1),1)
-		CC = clang
-	endif
 	ifeq ($(shell test "`expr "$(uname_R)" : '\([0-9][0-9]*\)\.'`" -ge 11 && echo 1),1)
 		HAVE_GETDELIM = YesPlease
 	endif