GitHub test.yml: add ubuntu-24.04-arm to matrix

[msgilligan]

GitHub has enabled arm64 runners for Open Source projects:
https://github.blog/changelog/2025-01-16-linux-arm64-hosted-runners-now-available-for-free-in-public-repositories-public-preview/

This is a naive attempt to turn it on for this project.

[sandydoo]

Neat! Looks like someone at GitHub made a typo in XDG_CONFIG_HOME 👀 I'll give them some time to roll out a new image and we'll try again.

[msgilligan]

Is there an open issue upstream for this?

[sandydoo]

Yeah, there's a couple with the same problem across multiple different actions.

Probably the correct one to upvote: actions/partner-runner-images#27

[msgilligan]

Issue #222 is how I discovered the problem.

[msgilligan]

The CI failure for this issue is currently:

https://github.com/cachix/install-nix-action/actions/runs/12817083173/job/35739671809?pr=221

Run cachix use cachix
  cachix use cachix
  shell: /usr/bin/bash -e {0}
  env:
    nixpkgs_channel: nixpkgs=channel:nixos-24.11
    oldest_supported_installer: nix-2.8.0
    NIX_PATH: nixpkgs=channel:nixos-24.11
    TMPDIR: /home/runner/work/_temp
cachix: /home/runneradmin/.config/nix: createDirectory: permission denied (Permission denied)
Error: Process completed with exit code 1.

[msgilligan]

I added a second commit with the suggested workaround from the upstream issue:

7e7bccb

[sandydoo]

There's no need to add a workaround. GitHub needs to update the image.

[msgilligan]

There's no need to add a workaround. GitHub needs to update the image.

Well, it would be nice to verify that the job runs to completion with the workaround. Then we can remove it before merging. I marked the PR as draft for now...

[msgilligan]

@sandydoo Upstream is fixed. I removed the workaround and force-pushed. I also marked as ready-for-review. 🤞