servo: deploy a service which periodically rebuilds my nix config to populate the cache

hosts/by-name/servo/services/default.nix

@@ -22,6 +22,7 @@
     ./monero.nix
     ./navidrome.nix
     ./nginx.nix
+    ./nixos-prebuild.nix
     ./nixserve.nix
     ./ntfy
     ./pict-rs.nix

hosts/by-name/servo/services/nixos-prebuild.nix

@@ -0,0 +1,22 @@
+{ pkgs, ... }:
+{
+  systemd.services.nixos-prebuild = {
+    description = "build a nixos image with all updated deps";
+    path = with pkgs; [ coreutils git nix ];
+    script = ''
+      working=$(mktemp -d /tmp/nixos-prebuild.XXXXXX)
+      pushd "$working"
+      git clone https://git.uninsane.org/colin/nix-files.git
+      cd nix-files
+      nix flake update
+      nix run '.#check' -- -j1 --cores 5
+      popd
+      rm -rf "$working"
+    '';
+  };
+
+  systemd.timers.nixos-prebuild = {
+    wantedBy = [ "multi-user.target" ];
+    timerConfig.OnCalendar = "11,23:00:00";
+  };
+}