What is the problem you're trying to solve
Support NOTIFY_SOCKET to support notifying the daemon's readiness to systemd.
This proposal does not relate to container tasks' lifecycles.

Describe the solution you'd like
Use https://github.com/coreos/go-systemd

Additional context
Like this: moby/buildkit@0dee033