build: Add SKIP_SET_METADATA flag

On some of the older devices the recovery doesn't support
metadata when setting permissions. This allows to use
set_perm vs set_metadata.
Enable this behavior by setting SKIP_SET_METADATA := true

Change-Id: Ib6cf97b5ca28cee8a87975231f3a61b156e77d29

Conflicts:
	core/Makefile