Cygwin 1.7 needs compat/regex

Cygwin v1.7 uses the regex library from newlib which does not pass git's
tests, so don't use it. This fixes failures in t4018 and t4034.

Continue to use the platform supplied regex library for earlier versions.

Signed-off-by: Mark Levedahl <mlevedahl@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.mak.uname

@@ -159,6 +159,8 @@ ifeq ($(uname_O),Cygwin)
 		NO_SYMLINK_HEAD = YesPlease
 		NO_IPV6 = YesPlease
 		OLD_ICONV = UnfortunatelyYes
+	else
+		NO_REGEX = UnfortunatelyYes
 	endif
 	NO_THREAD_SAFE_PREAD = YesPlease
 	NEEDS_LIBICONV = YesPlease