Use compatibility regex library also on FreeBSD

Commit 3632cfc24 makes the same change for Darwin; however, the problem
also exists on FreeBSD.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -677,6 +677,8 @@ ifeq ($(uname_S),FreeBSD)
 	BASIC_CFLAGS += -I/usr/local/include
 	BASIC_LDFLAGS += -L/usr/local/lib
 	DIR_HAS_BSD_GROUP_SEMANTICS = YesPlease
+	COMPAT_CFLAGS += -Icompat/regex
+	COMPAT_OBJS += compat/regex/regex.o
 endif
 ifeq ($(uname_S),OpenBSD)
 	NO_STRCASESTR = YesPlease