Add a fuzzer for OTA package verification

This is a pretty simplistic approach, it just shoves random data at the
verifier. The OTA format isn't too complicated so this should hopefully
be sufficient to let the fuzzer exercise the potentially interesting
parsing code.

Test: Let the fuzzer run on device for awhile:
      1) FUZZ=libinstall_verify_package_fuzzer
      2) SANITIZE_TARGET=hwaddress make ${FUZZ}
      3) cd ${ANDROID_PRODUCT_OUT} && adb root && adb sync data
      4) adb shell /data/fuzz/arm64/${FUZZ}/${FUZZ}
Change-Id: Icac6bde017b497d9f92c06191eb29e107ba9c0a7