Feat: build improvements

[patzm]

I had a brief look at the 🐳 docker based build setup. I found it a bit weird that the Docker-based approach would pull from the remote. For me, this would have made iterative work very cumbersome (push everytime I change someting). Also, any external contributor (like me) would need to change the base url of the GitHub repo (which external contributors have to fork).

Instead, it might be much easier to simply copy the current state of the repository into the docker container. The .gitignore prevents that unnecessary and maybe sensitive information from git finds its way there.

I also changed the folder name for the generated outputs to artifacts. Just an idea, reverting is simple.

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[patzm]

@googlebot I fixed it.

[google-cla]

We found a Contributor License Agreement for you (the sender of this pull request), but were unable to find agreements for all the commit author(s) or Co-authors. If you authored these, maybe you used a different email address in the git commits than was used to sign the CLA (login here to double check)? If these were authored by someone else, then they will need to sign a CLA as well, and confirm that they're okay with these being contributed to Google.
In order to pass this check, please resolve this problem and then comment @googlebot I fixed it.. If the bot doesn't comment, it means it doesn't think anything has changed.

ℹ️ Googlers: Go here for more info.

[patzm]

@googlebot I fixed it.