Add runner settings to get nix builds working

Committing this late (was already in use by system)

.forgejo/workflows/build_nixos_configs.yml

@@ -1,4 +1,4 @@
-name: Buill NixOS Configurations
+name: Build NixOS Configurations
 on: [push]
 
 jobs:

systems/x86_64-linux/gospel/default.nix

@@ -112,6 +112,15 @@
           "ubuntu-20.04:docker://node:16-bullseye"
           "ubuntu-18.04:docker://node:16-buster"
         ];
+        settings.container = {
+          options = ''
+            ;
+            -e PATH=:${pkgs.nix}/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
+            -e NIX_PATH=nixpkgs=flake:nixpkgs:/nix/var/nix/profiles/per-user/root/channels
+            -e NIX_REMOTE=daemon
+          '';
+          valid_volumes = [ "/nix" ];
+        };
       };
     };
   };