DexGenerator: allow specifying dex cache dir.

- Switches DexGenerator to not use extended opcodes.  This allows us to
  write suitable files for earlier versions of Android.
- Allows caller to specify optimised dex directory.  This allows us to
  get around /data/dalvik-cache not being world-writeable.
- Allows caller to specify optimised dex files cache dir.  This allows
  us to skip the requirement of being able to write to /sdcard.

Change-Id: I2cae2e187ccf5b20b98763cb7eb791383a7d5a59
3 files changed