Update scripts to support git checkouts of CEF and/or Chromium.

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk@1664 5089003a-bbd8-11dd-ad1f-f1f9622dbc98
Fix error in exec_util.py.

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk@1667 5089003a-bbd8-11dd-ad1f-f1f9622dbc98