Revert "Add the ability to pass use flags through cbuildbot to build_packages."

buildbot/cbuildbot_stages.py

Index: buildbot/cbuildbot_stages.py
diff --git a/buildbot/cbuildbot_stages.py b/buildbot/cbuildbot_stages.py
index 58fe388023e1a395d1483b4ce018f6bc387986f5..197a50bf0538cd024460df11592fb229698f92bc 100644
--- a/buildbot/cbuildbot_stages.py
+++ b/buildbot/cbuildbot_stages.py
@@ -319,14 +319,10 @@ class BuildTargetStage(BuilderStage):
     BuilderStage.new_binhost = self._GetPortageEnvVar(_FULL_BINHOST)
     emptytree = (BuilderStage.old_binhost and
                  BuilderStage.old_binhost != BuilderStage.new_binhost)
-    env=[]
-    if self._build_config['useflags']:
-      env.append('USE="%s"' % ' '.join(self._build_config['useflags']))
 
     commands.Build(
         self._build_root, emptytree, usepkg=self._build_config['usepkg'],
-        build_autotest=(self._build_config['vm_tests'] and self._options.tests),
-        extra_env=env)
+        build_autotest=(self._build_config['vm_tests'] and self._options.tests))
 
     # TODO(sosa):  Do this optimization in a better way.
     if self._build_type == 'full':