When the user has the `dind` service for [docker
build](https://docs.gitlab.com/ee/ci/docker/using_docker_build.html#use-docker-in-docker-workflow-with-docker-executor)
defined inside of the GitLab Runner `config.toml` they can set up the
`command` configuration what was
[introduced](https://gitlab.com/gitlab-org/gitlab-runner/-/issues/27173)
in GitLab Runner 13.6 to configure the mirror.