gclient: fix git version check to handle 1.6.5.2.5.g7c3ba.dirty

Review URL: http://codereview.chromium.org/486036

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@34386 0039d316-1c4b-4281-b951-d872f2087c98
1 file changed