am ff9aa9bf: am 9a2b2f76: Don\'t build dx if it\'s an app-only build.

Merge commit 'ff9aa9bfadcd4b17b078dfad65e0d700ea8c237a' into gingerbread-plus-aosp

* commit 'ff9aa9bfadcd4b17b078dfad65e0d700ea8c237a':
  Don't build dx if it's an app-only build.