image_signing: Add cr50 firmware signing support.

This introduces a script for signing Cr50 images on the build server.

BRANCH=cr50
TEST=sign_official_build.sh cr50_firmware input tests/devkeys output
BUG=b:74100307

Change-Id: I741b8532980b0a7a0b32fbacff235c38661c7668
Signed-off-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1313573
Commit-Ready: ChromeOS CL Exonerator Bot <chromiumos-cl-exonerator@appspot.gserviceaccount.com>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
3 files changed