TWRPify: Add parts to build TWRP

Change-Id: I02d1765178dd1b43cf180342a34e3a7c98475bf2
remove SKIP_SET_METADATA board flag.

 This is no longer needed with new TWRP recovery

Change-Id: I9f1e06a4fcde28c71854e18ac369a7d93da142f8