`/builds` is mounted to `/dev/nvme0n1p2[/var/lib/docker/volumes/runner-t1y-5gx5-project-34-concurrent-0-cache-c33bcaa1fd2c77edfc3893b41966cea8/_data` and given its name I don't think it's shared with another runner (or we have bigger problems than just the prefix because artifacts are extracted and run from there).