Check for circular dependencies between .gyp files.
Check for circular dependencies between .gyp files.

BUG=110
TEST=None yet
Review URL: http://codereview.chromium.org/373002
old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google,old8xp/gyp_from_google