set use_camera_stub

Change-Id: If8e69b8426a366c2ae19b5dddb8b43a1d6e3fe09
Fix overlays and setup proper append/init of PRODUCT_PACKAGES

Previously, Torch was not getting built due to conflicts and re-initialization
of some flags between the vendor and dev trees.

Change-Id: I7ecb0581c4abe8c5eb4082e6a276bc3e80168e03