monolith: add wopus gitlab runners

system/gitlab-runner.nix

@@ -1,18 +1,19 @@
 { pkgs, lib, ... }:
 {
   mkNixRunner =
-    authenticationTokenConfigFile: with lib; rec {
+    authenticationTokenConfigFile: with lib; {
       # File should contain at least these two variables:
       # `CI_SERVER_URL`
       # `REGISTRATION_TOKEN`
       inherit authenticationTokenConfigFile; # 2
       dockerImage = "alpine:3.18.2";
-      dockerAllowedImages = [ dockerImage ];
       dockerVolumes = [
         "/etc/nix/nix.conf:/etc/nix/nix.conf:ro"
         "/nix/store:/nix/store:ro"
         "/nix/var/nix/db:/nix/var/nix/db:ro"
         "/nix/var/nix/daemon-socket:/nix/var/nix/daemon-socket:ro"
+        "/var/run/docker.sock:/var/run/docker.sock"
+        "/cache"
       ];
       dockerDisableCache = true;
       preBuildScript = pkgs.writeScript "setup-container" ''
@@ -36,6 +37,7 @@
               cacert
               git
               openssh
+              docker
             ]
           )
         }