Cross compilation ready Dockerfile (for arm images)

[AFCMS]

Follows #14230

Problem

Currently the image built by the CI only works on amd64 architecture, GitHub Actions doesn't provide ARM runners to build a ARM images natively.

ARM images would be pretty useful for RasberryPI servers, and there are a lot of other platforms supported by Alpine which could benefit from an official image.

Solutions

There are three ways to build ARM images:

• QEMU based, Docker buildx supports it quite well, but GitHub Actions runners don't enable virtualisation acceleration so the build takes a loooong time (more than one hour)
• Cross compilation support in the Dockerfile
• Wait for GitHub to provide non-M1 ARM runners

While cross compilation is easy when it comes to Rust or Go, it's a bit harder for C/C++.

There is this project by a Docker employee which makes things a bit easier: https://github.com/tonistiigi/xx

Alternatives

Do nothing, leave people on ARM hardware build the image themselves.

Additional context

No response

[suryaoruganti]

You can use WarpBuild for natively provided arm64 runners.

It'll help speed up those builds.
Note: I'm the founder.

[AFCMS]

I think its ultimately better to setup cross-compilation, it could benefit to people who want to test locally or deploy a custom Minetest build onto an ARM PC.

I am currently working on it 👍

[AFCMS]

Apparently GitHub started deploying non-M1 ARM runners with a private beta for enterprises and apparently some open-source projects have access already to them. 🥳

For reference if Minetest get access: https://docs.docker.com/build/ci/github-actions/multi-platform/#distribute-build-across-multiple-runners