Introduce multi-arch builds with support for ARM

[aiven-anton]

About this change - What it does

With this commit we start building multi-arch container images to enable running containers on ARM systems.

Closes #521.

References #585.

Why this way

I did experimentation/debugging in this repository: https://github.com/aiven-anton/test-build-arm, see results of build 12 and 13.

Using the Docker actions makes for very low amount of boilerplate code for building containers.

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[tvainika]

I suspect this does not work.

Sadly our container builds from GitHub Actions are triggered only on main branch. Therefore no container CI action was triggered by this pull request. Therefore I pushed this branch into my own fork's main branch, and this resulted build failure https://github.com/tvainika/karapace/actions/runs/4675463034

I think build failure is because Gather context step does not have all tags with fetched history. Actions/checkout needs fetch-depth flag to fetch all tags.

[aiven-anton]

Sadly our container builds from GitHub Actions are triggered only on main branch.

Perhaps I should start in this end, building an image for PRs and adding some very basic smoke test. That would probably make it easier to gain confidence for a PR like this one later on. Very good idea that you tried this out on a fork! 🙏

The failure is a bit odd though, the $(git describe --always) from the "Gather context" step was taken as-is from the current "Build and push container image" step, and checkout hasn't changed so I think if git history/tags is too shallow now, it must have been before too. I think what's triggering this is the explicit passing of KARAPACE_VERSION, which means Karapace is no longer attempting to gather the version from git itself. Inspecting the line where it used to, it's clear that's a different invocation than in "Gather context": it has --tags.

I'll put this PR in draft for now, and will try to come back to it once we have smoke tests 🙂

[aiven-anton]

@tvainika I managed to get the build working on my fork now, I did these things:

• Make sure there are actually tags in the repository (did not get cloned by default).
• Set fetch-depth: 0 as you suggested.
• Add --tags to git describe invocation.

Passing build: https://github.com/aiven-anton/karapace/actions/runs/4872183301/jobs/8690049653