Enhancement: Link `/repo/` to `/github/workspace/`

[localheinz]

This pull request

• [x] creates a /github/ directory and a symbolic link from /repo/ to /github/workspace/

💁‍♂️ I am unsure how to mount a volume when using a Docker image in a GitHub Actions step. However, as you can see in https://github.com/ergebnis/playground/actions/runs/4053829531/jobs/6974917526#step:10:13, GitHub mounts the GitHub workspace directory, e.g., /home/runner/work/playground/playground to /github/workspace, so by creating a symbolic link from /github/workspace to /repo should make the failing workflow referenced above pass.

What do you think?

[localheinz]

Not sure if that even makes sense.

[theseer]

I understand the reasoning but no:

• This would make the image github specific for no other reason than not finding out how to arbitrarily map volumes ;)
• This would make it hard to use for any non-github use case
• This also wouldn't work as is, since adding it to the build Containerfile doesn't suffice. We still need would to adopt it into the stripped image (see build.xml)

What we could consider doing is creating a dedicated image on ghcr.io for this purpose, based on the "offical" build image (we can't use the stripped image because it doesn't contain mkdir and ln). I wouldn't know how to do that though as of yet ;)