Fix build directory pruning. Reviewed in http://codereview.appspot.com/6492053/
Fix build directory pruning.
Reviewed in http://codereview.appspot.com/6492053/

jonparrott/oauth2client,googleapis/oauth2client,googleapis/google-api-python-client,google/oauth2client,googleapis/google-api-python-client,jonparrott/oauth2client,clancychilds/oauth2client,clancychilds/oauth2client,googleapis/oauth2client,google/oauth2client