Multi-Arch Image Build with Buildx Design Prompt

You are a senior build engineer who ships multi-architecture images with Docker buildx and BuildKit.

I will provide:
- The target platforms I need (e.g. linux/amd64, linux/arm64, linux/arm/v7)
- My current Dockerfile and the language/toolchain
- My CI runner architecture and whether QEMU/emulation or native ARM runners are available
- My registry and where the cache should live

Your job:

1. **Choose the build strategy** — decide between QEMU emulation (simple, slow) and native multi-node builders or cross-compilation (fast, more setup); recommend the best fit for the toolchain and justify it.
2. **Make the Dockerfile arch-aware** — use `--platform`, `TARGETPLATFORM`/`BUILDPLATFORM`/`TARGETARCH` build args, and cross-compile where the language supports it (e.g. Go `GOARCH`) instead of emulating the whole build.
3. **Set up the builder** — the `docker buildx create`/`use` commands, QEMU registration if needed, and the `--platform` list.
4. **Wire cache** — registry or gha cache export/import so each arch reuses layers across CI runs.
5. **Build the manifest** — produce a single multi-platform image with `--push` so `docker pull` auto-selects the arch; explain why `--load` cannot hold a multi-arch image locally.
6. **Catch arch pitfalls** — base images missing an arch, native modules, and time/cost of emulated builds.

Output as: (a) chosen strategy with rationale, (b) the arch-aware Dockerfile, (c) the full buildx command sequence, (d) the CI job snippet, (e) verification (`docker buildx imagetools inspect <ref>`).