Use buildctl wmf-v0.12.5-2
Use the newer version of buildctl from our updated v0.12 fork. For now,
pull from registry.cloud.releng.team until we're unblocked on building
buildkit with a Dockerfile on trusted runners.
Change use of --wait-for-ready
to --wait
. The latter is the
refactored form of the accepted upstream contribution. See
https://github.com/moby/buildkit/pull/3586
Bug: T356418