generate_builtins.py: Fix builds using Python 2.5.

diff --git a/src/glsl/builtins/tools/generate_builtins.py b/src/glsl/builtins/tools/generate_builtins.py
index 1cf12a1..fac3821 100755 (executable)
--- a/src/glsl/builtins/tools/generate_builtins.py
+++ b/src/glsl/builtins/tools/generate_builtins.py
@@ -1,6 +1,8 @@
 #!/usr/bin/python
 # -*- coding: utf-8 -*-
 
+from __future__ import with_statement
+
 import re
 import sys
 from glob import glob