Only apply the test-driver patch if nixpkgs doesn't have it yet.

nix/lib.nix

@@ -441,10 +441,22 @@ in
           upstream = hostPkgs.callPackage "${nixpkgs}/nixos/lib/test-driver" { };
         in
         upstream.overrideAttrs (_: {
-          # Until github.com/NixOS/nixpkgs#228220 gets merged
-          patches = [
-            ../test/0001-nixos-test-driver-include-a-timeout-for-the-recv-cal.patch
-          ];
+          # Try to apply the patch for backwards compat.
+          # It is included upstream starting from NixOS 23.05.
+          # github.com/NixOS/nixpkgs#228220
+          postPatch =
+            let
+              patch = "${lib.getBin hostPkgs.patch}/bin/patch";
+              patchFile = ../test/0001-nixos-test-driver-include-a-timeout-for-the-recv-cal.patch;
+            in
+            ''
+              echo "Try to apply patch ${patchFile}..."
+              if ${patch} --reverse -p1 --silent --force --dry-run --input=${patchFile}; then
+                echo "Patch already present, ignoring..."
+              else
+                ${patch} -p1 < ${patchFile}
+              fi
+            '';
         });
 
       runTest = { nodes, vlans, testScript, extraDriverArgs }: ''

test/0001-nixos-test-driver-include-a-timeout-for-the-recv-cal.patch

@@ -79,15 +79,5 @@ index 9de98c217a5..4b34ac423d1 100644
              toc = time.time()
 
              self.log("connected to guest root shell")
-@@ -950,7 +966,7 @@ class Machine:
-         Prepares the machine to be reconnected which is useful if the
-         machine was started with `allow_reboot = True`
-         """
--        self.send_key(f"ctrl-alt-delete")
-+        self.send_key("ctrl-alt-delete")
-         self.connected = False
- 
-     def wait_for_x(self) -> None:
 --
 2.39.2
-