gitlab runner config to run under nixos with shared nix store

config.toml

concurrent = 32
check_interval = 3
[[runners]]
  name = "ci"
  url = "https://gitlab.com/ci"
  token = "${gitlab_runner_token}"
  executor = "docker"
  environment = ["NIX_REMOTE=daemon", "NIX_PATH=nixpkgs=/nix/var/nix/profiles/per-user/root/channels/nixpkgs"]
  pre_build_script = "export PATH=$PATH:/run/current-system/sw/bin; unset SSL_CERT_FILE; unset GIT_SSL_CAINFO"
  [runners.docker]
    tls_verify = false
    image = "nixos/nix"
    privileged = false
    disable_cache = true
    volumes = ["/nix:/nix:ro", "/run/current-system/sw:/run/current-system/sw:ro", "/nix/var/nix/daemon-socket/socket:/nix/var/nix/daemon-socket/socket", "/etc/ssl/certs/ca-certificates.crt:/etc/ssl/certs/ca-certificates.crt:ro"]