Problem

overlaybd-snapshotter cannot created overalybd snapshot when the Dockerfile depends on OCI image.

Problem Detail

Currently overlaybd-snapshotter can create overlaybd image on the top of OCI image, which is not working. The blueprint image format looks like below.

If it's working, the blueprint image format looks like this

As you can see, it should shows overlaybd annotation.

Root Cause

Here is the buildkit open source.
https://github.com/moby/buildkit/blob/master/cache/blobs.go#L190-L202
Currently, Runloop uses overlaybd snapshooter whose name is "overlaybd". buildkit open sources probably assumes it's not overlaybd image, because of this line of code.
if bdPath := snStat.Labels[obdlabel.LocalOverlayBDPath]; bdPath != "" {

What does this PR do

This PR supports to support the issue above.

What's the limitation of this PR

This PR attach overlaybd annotation onto the image format. However, first layer doesn't contain it.

What this PR does / why we need it:

Which issue(s) this PR fixes (optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close the issue(s) when PR gets merged):
Fixes #

Please check the following list:

• Does the affected code have corresponding tests, e.g. unit test, E2E test?
• Does this change require a documentation update?
• Does this introduce breaking changes that would require an announcement or bumping the major version?
• Do all new files have an appropriate license header?