Consider adding support for arm64

[tchajed]

It would be great to start building arm64 images. I have two use cases:

• I like to provide my students with a Docker image so they don't have to install Rocq. Almost any student on a Mac is on arm64 and for reasonable performance needs a matching image. Currently I solved this problem by building my own images directly from debian, but I don't want to maintain that.
• I recently learned that GitHub arm64 runners are now in public preview, and they seem to have better performance than the x86 runners (I did a not-very-scientific test but the difference was 1h 30m vs 1h 4m real-time and 20,000 CPU-seconds vs 15,000 CPU-seconds).

There is some way to create multi-arch images on Docker hub, but I don't really understand it - I've just been using docker buildx and emulating the x86 build on an arm64 mac.

[Zimmi48]

Did you look into whether docker-keeper would work for generating these arm64 images?

[tchajed]

I think this is a feature to be added to docker-keeper. As I understand, it generates a matrix of Dockerfiles for a number of configs, then builds all of them. A multi-arch build requires first generating the underlying Dockerfiles and then (I believe) some sort of manifest file to group them into one tag on Docker hub. See this blog post: https://www.docker.com/blog/multi-arch-build-and-images-the-simple-way/.