Makefile: fix default regex settings on Darwin

t0070-fundamental.sh fails on Mac OS X 10.8:

	$ uname -a
	Darwin lustrous 12.2.0 Darwin Kernel Version 12.2.0:
	Sat Aug 25 00:48:52 PDT 2012;
	root:xnu-2050.18.24~1/RELEASE_X86_64 x86_64

	$ ./t0070-fundamental.sh -v
	fatal: regex bug confirmed: re-build git with NO_REGEX=1

Fix it by using Git's regex library.
Reviewed-by: NJonathan Nieder <jrnieder@gmail.com>
Signed-off-by: NDavid Aguilar <davvid@gmail.com>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Makefile

@@ -1054,6 +1054,7 @@ ifeq ($(uname_S),Darwin)
 			BASIC_LDFLAGS += -L/opt/local/lib
 		endif
 	endif
+	NO_REGEX = YesPlease
 	PTHREAD_LIBS =
 endif