Mac: Fix ninja build (issue #922)

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef3@1192 5089003a-bbd8-11dd-ad1f-f1f9622dbc98
- Windows: Fix ninja build (issue #922).
- Update make_distrib.py to support ninja builds via a new "ninja-build" flag (issue #922).

git-svn-id: http://chromiumembedded.googlecode.com/svn/trunk/cef3@1193 5089003a-bbd8-11dd-ad1f-f1f9622dbc98