scons: Control caching via new SCONS_CACHE_DIR environment variable.

This serves several purposes:
- disable caching in situations were is it useless or undesired
- share caches among all trees
- simplify purging the cache (when it's a single location)
- move the cache out of the tree, since that slows downs IDEs considerably

To retain previous behavior just define do

  export SCONS_CACHE_DIR=$PWD/build/cache

before invoking scons.

1 files changed, 3 insertions, 1 deletions

diff --git a/scons/gallium.py b/scons/gallium.py
index 633b86bd698..d3bd419fb3e 100644
--- a/scons/gallium.py
+++ b/scons/gallium.py
@@ -235,7 +235,9 @@ def generate(env):
     # different scons versions building the same source file
     env['build'] = build_dir
     env.SConsignFile(os.path.join(build_dir, '.sconsign'))
-    env.CacheDir('build/cache')
+    if 'SCONS_CACHE_DIR' in os.environ:
+        print 'scons: Using build cache in %s.' % (os.environ['SCONS_CACHE_DIR'],)
+        env.CacheDir(os.environ['SCONS_CACHE_DIR'])
 
     # Parallel build
     if env.GetOption('num_jobs') <= 1: