--- glew-1.10.0.orig/Makefile	2013-07-22 16:11:22.000000000 +0200
+++ glew-1.10.0/Makefile	2013-07-30 13:16:20.000000000 +0200
@@ -71,7 +71,8 @@ else
 OPT = $(POPT)
 endif
 INCLUDE = -Iinclude
-CFLAGS = $(OPT) $(WARN) $(INCLUDE) $(CFLAGS.EXTRA)
+CFLAGS ?= $(OPT) $(WARN) $(CFLAGS.EXTRA)
+CFLAGS += $(INCLUDE)
 
 all debug: glew.lib glew.lib.mx glew.bin