Add script to sign Android image

sign_android_image.sh is the main script that signs the image. It makes
similar changes to an image like the Android official signing tool
(sign_target_files_apks.py) does, but more Chrome OS specific.

TEST=./sign_official_build.sh recovery recovery_image.bin \
         ../../tests/devkeys/ out_img
TEST=Same above but with a recovery image without Android image.
     Android signing was skipping.
TEST=Same above but with a M53 image.  Android signing was skipped.
TEST=Unpack the image and diff the before and after.  Looks correct.
BUG=b:29915721

Change-Id: I0ae5f0ad8d2b05e485d60262558517ea563bf527
Reviewed-on: https://chromium-review.googlesource.com/366794
Commit-Ready: Victor Hsieh <victorhsieh@chromium.org>
Tested-by: Victor Hsieh <victorhsieh@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
11 files changed