Create build-superimage-target.

Combine INSTALLED_SUPERIMAGE_TARGET with INSTALLED_SUPERIMAGE_EMPTY_TARGET.

Also fixes inconsistent UUIDs for super_empty.img
because PRIVATE_SUPER_PARTITION_SUFFIX is not defined.

Test: flash and inspect device mapper
Change-Id: I7f00c4e21ebdd21e94fa387c6e2fbea06a6e75b7