tf/hydra: add a test staging-small nixpkgs jobset

terraform/hydra.nix

@@ -71,5 +71,45 @@ in
         }
       ];
     };
+
+    resource.hydra_jobset.delroth-nixpkgs-staging-small = {
+      project = config.resource.hydra_project.forkos.name;
+      state = "enabled";
+      visible = true;
+      name = "delroth-nixpkgs-staging-small";
+      type = "legacy";
+      description = "small eval of nixpkgs staging for testing";
+
+      nix_expression = {
+        file = "pkgs/top-level/release-small.nix";
+        input = "nixpkgs";
+      };
+
+      check_interval = 0;
+      scheduling_shares = 3000;
+      keep_evaluations = 3;
+
+      email_notifications = false;
+
+      input = [
+        {
+          name = "nixpkgs";
+          type = "git";
+          value = "https://github.com/nixos/nixpkgs staging";
+          notify_committers = false;
+        }
+        {
+          name = "officialRelease";
+          type = "boolean";
+          value = "false";
+          notify_committers = false;
+        }
+        {
+          name = "supportedSystems";
+          type = "nix";
+          value = ''[ "x86_64-linux" ]'';
+        }
+      ];
+    };
   };
 }