Is a self-hosted Windows runner even possible?

Hi!

I'm currently trying to set up a bare-metal, self-hosted Windows runner for workflows using unity-builder@v4.
However, I keep running into issues and I'm starting to wonder if it's been futile from the start.

I'm a bit confused by the documentation in regards to this. The guide for setting up a self hosted runner in the Game-CI docs makes no mention of windows at all and the GitHub Actions documentation states [here](https://docs.github.com/en/actions/hosting-your-own-runners/managing-self-hosted-runners/about-self-hosted-runners#requirements-for-self-hosted-runner-machines) that _"you must use a Linux machine"_ to use actions utilizing docker containers. (Which I assume refers to actions such as this.)

For a little more context, I'm running into this error:
```cmd
...
Building locally
"C:\Program Files\Docker\Docker\resources\bin\docker.exe" run --workdir c:/github/workspace --rm ((flags omitted for brevity)) powershell c:/steps/entrypoint.ps1
docker: Error response from daemon: the working directory 'c:/github/workspace' is invalid, it needs to be an absolute path.
See 'docker run --help'.
Error: Build failed with exit code 125
```

This error does not occur when running the same workflow on a GitHub-hosted Windows runner.
I'm not sure if this is an issue I can fix on my end or if there is some magic happening with GitHub's runners that I don't understand.

Start with the Game-CI self-hosted runner guide and the GitHub Actions self-hosted runner requirements linked in the issue. Reproduce the unity-builder@v4 workflow on a bare-metal Windows runner and inspect the Docker working-directory error. Done means establishing whether this setup is supported and documenting the limitation or required configuration.

Written by the indexing model from the issue text.