gitlab-runner: pin nixpkgs version in jobs

system/gitlab-runner.nix

@@ -1,4 +1,9 @@
-{ pkgs, lib, ... }:
+{
+  pkgs,
+  lib,
+  inputs ? null,
+  ...
+}:
 let
   installNixScript =
     {
@@ -78,6 +83,7 @@ rec {
         USER = "root";
         NIX_REMOTE = "daemon";
         NIX_SSL_CERT_FILE = "/nix/var/nix/profiles/default/etc/ssl/certs/ca-bundle.crt";
+        NIX_PATH = if inputs != null then "nixpkgs=${inputs.nixpkgs}" else "";
       };
     };
 

system/monolith-gitlab-runner.nix

@@ -1,10 +1,11 @@
 {
   config,
   pkgs,
+  inputs,
   ...
 }:
 let
-  inherit (pkgs.callPackage ./gitlab-runner.nix { }) mkNixRunner mkNixRunnerFull;
+  inherit (pkgs.callPackage ./gitlab-runner.nix { inherit inputs; }) mkNixRunner mkNixRunnerFull;
 in
 {
   boot.kernel.sysctl."net.ipv4.ip_forward" = true;