cgcc: define __APPLE_CC__ on OSX

It seems that some header files somehow need this.

Signed-off-by: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
diff --git a/cgcc b/cgcc
index 629124b..7393947 100755
--- a/cgcc
+++ b/cgcc
@@ -273,7 +273,7 @@
 	    ' -D__NetBSD__=1';
     } elsif ($spec eq 'darwin') {
 	return
-	    ' -D__APPLE__=1 -D__MACH__=1';
+	    ' -D__APPLE__=1 -D__APPLE_CC__=1 -D__MACH__=1';
     } elsif ($spec eq 'gnu') {		# Hurd
 	return &add_specs ('unix') .	# So, GNU is Unix, uh?
 	    ' -D__GNU__=1 -D__gnu_hurd__=1 -D__MACH__=1';