GitLab CI: stop uploading the whole build dir as an artifact

In fd8cc96a we introduced ci-static-analysis.yml with GitLab jobs to run clazy. The normal build job uploads its 'build' directory as an artifact and the static-analysis job then uses that artifact and runs clazy on it.

Making the entire 'build' directory an artifact is making all builds take very long and sometimes even timeout, even if they don't use static analysis. This commit removes 'build' as an artifact in ci-before.yml. Projects using the static analysis job will have to explicitly add it back.

I already sent utilities/keysmith!65 (merged), which seemed to be the only main-namespace repo currently using it.

Ideally we should find a way to run clazy without having to pass artifacts between jobs, eg. run it on the same job as the compilation...