This allows cache_dir to be enabled on bots when the individual repo path has
changes (like android_tools, which has a bunch of generated, non-ignored .h
files)

R=agable@chromium.org, szager@chromium.org
BUG=

Review URL: https://codereview.chromium.org/488273003

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@290943 0039d316-1c4b-4281-b951-d872f2087c98