http://bugs.gentoo.org/234599

--- MRULES
+++ MRULES
@@ -1,8 +1,8 @@
 # Standard compilation rules (don't use make builtins)
 
 %.o: %.c
-	$(CC) $(CFLAGS) $< -c
+	$(CC) $(CFLAGS) $(CPPFLAGS) $< -c
 
 %.o: %.cc
-	$(CC) $(CFLAGS) $< -c
+	$(CC) $(CFLAGS) $(CPPFLAGS) $< -c