Docker Build Cloud

Operator wants Docker Build Cloud builds from CI. CI currently uses the default 'docker' driver which only builds for the runner's architecture.

Run 'docker buildx create --driver cloud <org>/<builder-name> --use'. Subsequent 'docker buildx build' streams the build to the cloud builder endpoint; native ARM and amd64 stages run on dedicated hardware (no QEMU). Authenticate to Docker Hub first (docker login).

Team builds Python+native-deps images for both linux/amd64 and linux/arm64. Local QEMU build for ARM takes 12 min; native ARM stage from CI ~2 min.

Run 'docker buildx build --builder <cloud> --platform linux/amd64,linux/arm64 --push'. Build Cloud executes amd64 stages on amd64 hosts and arm64 stages on arm64 hosts — no emulation. Net speedup is workload-dependent [REQUIRES-VERIFICATION on the 6x figure].

Developer A and developer B run the same build with identical deps. A's build is cold; B (later) gets a cache hit by sharing the cloud builder.

Build Cloud maintains per-builder cache shared across all users of that builder. Both A and B target the same <org>/<builder>; B's overlapping layers are imported from cache. Verify in build output (CACHED lines). Cache eviction policy is provider-managed.