am fb0a347b: Disable building OTA package if there is no kernel.

Merge commit 'fb0a347b747a91173c8a9f845a0362e3f8a9701f' into gingerbread-plus-aosp

* commit 'fb0a347b747a91173c8a9f845a0362e3f8a9701f':
  Disable building OTA package if there is no kernel.