--- configure.orig	2013-02-08 23:35:50.000000000 +0900
+++ configure	2013-02-15 20:51:52.000000000 +0900
@@ -15909,8 +15909,8 @@
 fi
 
 if test -n "$GCC"; then
-   CFLAGS="-O3 -Wall";
-   CXXFLAGS="-O3 -Wall";
+   CFLAGS="$CFLAGS -Wall";
+   CXXFLAGS="$CXXFLAGS -Wall";
 fi