archlinux CI is failing with "shell not found"

Archlinux CI is currently failing with "shell not found".

E.g. https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/jobs/29095

Apparently this comes from https://gitlab.com/gitlab-org/gitlab-runner/-/blob/master/shells/bash.go#L18 and it seems to be related to the latest archlinux docker image update.

I also tried to manually set the entrypoint b5cd874a, but it still fails with a different error message https://gitlab.steamos.cloud/steamrt/steam-runtime-tools/-/jobs/29110

After further investigation I found a discussion and a bug report upstream regarding this issue https://bbs.archlinux.org/viewtopic.php?pid=1954500 and https://bugs.archlinux.org/task/69563.