check-builtins: strip executable suffix $X when enumerating builtins

On Windows, the builtin executable names are suffixed with $X.

Signed-off-by: Sebastian Schuberth <sschuberth@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

check-builtins.sh

@@ -3,7 +3,7 @@
 {
 	cat <<\EOF
 sayIt:
-	$(foreach b,$(BUILT_INS),echo XXX $b YYY;)
+	$(foreach b,$(BUILT_INS),echo XXX $(b:$X=) YYY;)
 EOF
 	cat Makefile
 } |