Set --ninja_suffix based on make/mm/mmm targets

This fixes two issues:

- Switching make target didn't work well when the latter
  make target is not a subset of the first make target.
- Switching between m and mm/mmm forced build.ninja to be
  regenerated.

Bug: 23685536

Change-Id: I3c3550d6cca3007d166a13367d6bc22cc3feede2