secrets: allow providing secrets with env

[quasis]

Now that buildkit supports the feature (moby/buildkit#1534) will be awesome to have it in compose as well.

Possible syntax:

secrets:
    some_secret_name:
        env: SOME_ENV_VARIABLE

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.

[stale]

This issue has been automatically closed because it had not recent activity during the stale period.

[lsorber]

May I request to reopen this issue?

This feature would be a great complement to the recently added build time secrets feature.

[rmcclaincf]

I would also like to see this reopened. We are migrating our Jenkins to build images using secrets from env vars. Not having this feature is going to require us to make extensive workarounds to make our images build both locally and in our pipelines.

[glours]

@rmcclaincf this feature has been added a couple of month ago.