83beaff2db
The buildkit_config setting does not exist in the plugin-docker-buildx build we run: the binary has no PLUGIN_BUILDKIT_CONFIG, so the block was dead YAML and `docker buildx create` ran without --config, leaving the spawned buildkit container with no internal CA. The plugin only writes a buildkit.toml (pointing at /etc/docker/certs.d/<registry>/ca.crt) when `registry` is set. Set registry on the build step, drop the dead block from every step, and fail ci/check-distros.sh when a matrix value restating a distro.env key drifts from it.