gallium: Add SCons as alternative build system for Gallium.
diff --git a/.gitignore b/.gitignore
index 033e6e1..bf50291 100644
--- a/.gitignore
+++ b/.gitignore
@@ -7,3 +7,5 @@
 depend.bak
 lib
 lib64
+.sconsign*
+config.py