remove non-AOSP build files (except kernel.mk)

Change-Id: I59ea01a100dbd91a2bd3983e54ff0beb138b4e64
reset main.mk

Change-Id: Id317a5196600cc19ed061248b79a8214fb5712a9
reset a bunch more AOSP build files

Change-Id: I6f630f978753a904317a8dd1e984d677e8aa2963