cros_generate_update_payload: output payload metadata size

We need to get the update payload metadata size somehow for paygen
tests. This is the best way to do it. This patch adds
out_metadata_size_file flag to cros_generate_update_payload.

BUG=chromium:808495
TEST=unittest pass; payload tryjob

Change-Id: I65c48565afbdfaff619d6ac08bd8d36a8fb59315
Reviewed-on: https://chromium-review.googlesource.com/912102
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
1 file changed