Make mkbootimg a py_binary. Bug: 433545832 (cherry picked from https://googleplex-android-review.googlesource.com/q/commit:9cb122497de8a9083495b09b4c470834d8834aaa) Merged-In: I51cca9384a05aab89898844d99e1697d15f9a383 Change-Id: I51cca9384a05aab89898844d99e1697d15f9a383