Always write the metadata revisions for each layer into a machine-
readable "metadata-revs" file so that you can potentially link changes
in the output back to changes in the metadata. (Unlike the existing
similar build-id file, this is not specific to image changes.)
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
