Allow building non-amd64 Docker images

[cap10morgan]

These changes allowed me to build arm Docker images to run on my Raspberry Pi. I used the new docker buildx feature to cross-build them. Let me know how else you'd like that documented / integrated into this repo.

The images I built are hosted here: https://hub.docker.com/repository/docker/cryptorado/go-ipfs

[Stebalien]

Thanks!

And yes, documentation (in the docker section of the readme) would be most welcome.

[cap10morgan]

@Stebalien Thanks for merging! Since this is about building multi-arch images (rather than using the pre-built images which is what that section of the readme is about), is there some way I can help get the official images building arm64 and armv7 variants?

[Stebalien]

We just let docker hub auto-build from github. I'm not sure how to convince docker hub to build cross-platform.

[mburns]

https://hub.docker.com/r/ckulka/multi-arch-example seems like a reasonable guide.

I don't have permission to view/make changes on the Hub side, fwiw, but this seems straightforward if there is interest in making it happen.

[Stebalien]

Nice!

Github version: https://github.com/ckulka/docker-multi-arch-example

I wonder if there's any way to avoid duplicating the docker file.

---

@mburns I've given you the correct permissions, I think. Go for it (when you have time).