scons: Make command line arguments effective again.
diff --git a/SConstruct b/SConstruct
index 8013e7c..6f95d12 100644
--- a/SConstruct
+++ b/SConstruct
@@ -33,18 +33,16 @@
 	default_statetrackers = 'mesa'
 	default_drivers = 'softpipe,failover,i915simple,i965simple'
 	default_winsys = 'xlib'
-	default_dri = 'yes'
 elif common.default_platform in ('winddk',):
 	default_statetrackers = 'none'
 	default_drivers = 'softpipe,i915simple'
 	default_winsys = 'none'
-	default_dri = 'no'
 else:
 	default_drivers = 'all'
 	default_winsys = 'all'
-	default_dri = 'no'
 
-opts = common.Options()
+opts = Options('config.py')
+common.AddOptions(opts)
 opts.Add(ListOption('statetrackers', 'state_trackers to build', default_statetrackers,
                      ['mesa']))
 opts.Add(ListOption('drivers', 'pipe drivers to build', default_drivers,