am 83f69eb5: Prepend ccache to CC/CXX if necessary.

Merge commit '83f69eb5f905d47581bed141b7f5103362390339' into gingerbread-plus-aosp

* commit '83f69eb5f905d47581bed141b7f5103362390339':
  Prepend ccache to CC/CXX if necessary.