User Docker-in-Docker to build images
Our pipelines seem to be largely prepared for using Docker itself to build the images.
However, they fail when actually executing them with the Docker runner
Warning: failed to get default registry endpoint from daemon (Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?). Using system default: https://index.docker.io/v1/
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
Thus, they currently have to be tagged as shell
rather than Docker. In the long run, I think it would be nice if would not depend on the shell runner anymore.
Docker-in-Docker instructions: https://docs.gitlab.com/ee/ci/docker/using_docker_build.html