Explore the possibility of not storing cache locally when an object storage is configured for runner
When an object storage is configured to store cache for runner, we still store it locally (e.g. at
/home/gitlab-runner/cache/ for shell runner).
It can potentially cause disk space issues on the runner host (happened for one of our customers in this internal Zendesk ticket).
Don't store cache locally when an object storage is configured, make it configurable, or allow periodically clean it up.