Slight changes in Makefile

- generate CUSTOM_TARGET_PACKAGE: this makes the rom name to appear and the zip not being copied to the root directory
- generate zip's md5

Change-Id: Ib055309ae70dc5e8e7b217463bbb880569ff1650
change md5sum to md5

Change-Id: I404349a3d6b48d83f45776a749f6c5a84565a047