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

Merge commit '9a2b2f7678128a5385c83ea393d73cf3cdfcbe46' into gingerbread

* commit '9a2b2f7678128a5385c83ea393d73cf3cdfcbe46':
  Don't build dx if it's an app-only build.