Prevent git commands in dangerous dirs

[ofalvai]

Checklist

• [ ] I've read and followed the Contribution Guidelines
• [ ] step.yml and README.md is updated with the changes (if needed)

Version

Requires a MAJOR/MINOR/PATCH version update

Context

Even though this step is run_if: .IsCI, running it on an incorrectly configured self-hosted agent could do ugly things.

Changes

Match clone_into_dir against a list if known dangerous directories and abort the execution before the first real git command.