Change default output directory to use file dir.

It is not quite necessary to specify the external cache as the output
directory per discussion with bennolin@ months ago. For instrument
tests, we could just leverage the context's file dir.

Test: Unit test and http://ab/I82300010077210822
Change-Id: I4c648da095eb2671a7b8667897818683edf0196c
1 file changed
tree: ce1e9944b6d9f6bc2e79be55582473a4c49bc259
  1. build/
  2. docs/
  3. emu_test/
  4. libraries/
  5. scripts/
  6. tests/
  7. utils/
  8. PREUPLOAD.cfg