add phony target "all_modules" and use it as make goal for "mm"/"mmm"

So that mm/mmm don't depend on phony target "files", which brings in
unwanted files for apps-only build.
Also allow "dist" for mmm.
Bug: http://b/issue?id=2811503

Change-Id: I2c0794aebd1d171d8a0f44eb8cda67855704d6bd