Add a "cleanup" step so that errors from runtest.py are kept in thier own build step.

NOTRY=true

Review URL: https://codereview.chromium.org/122623002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@242743 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 242743