xfce.mkXfceDerivation: Deprecate

All Xfce packages are meson-only in 4.22 and there really are no Xfce
specific bits involved in packaging that worth keeping mkXfceDerivation.

doc/release-notes/rl-2605.section.md

@@ -9,6 +9,11 @@
 
 <!-- To avoid merge conflicts, consider adding your item at an arbitrary place in the list instead. -->
 
+- `xfce.mkXfceDerivation` has been deprecated, please use `stdenv.mkDerivation`
+  directly. You can migrate by adding `pkg-config`, `xfce4-dev-tools`, and
+  `wrapGAppsHook3` to your `nativeBuildInputs` and `--enable-maintainer-mode`
+  to your `configureFlags`.
+
 - `corepack_latest` has been removed, as Corepack is no longer distributed with Node.js.
 
 - `spoof` has been removed, as there are many issues upstream with it working on modern OS versions, and it appears to be unmaintained.

pkgs/desktops/xfce/default.nix

@@ -19,8 +19,6 @@ makeScopeWithSplicing' {
 
       genericUpdater = pkgs.genericUpdater;
 
-      mkXfceDerivation = callPackage ./mkXfceDerivation.nix { };
-
       #### CORE
 
       exo = callPackage ./core/exo { };
@@ -169,6 +167,13 @@ makeScopeWithSplicing' {
 
       automakeAddFlags = throw "xfce.automakeAddFlags has been removed: this setup-hook is no longer used in Nixpkgs"; # added 2024-03-24
 
+      mkXfceDerivation = lib.warnOnInstantiate ''
+        xfce.mkXfceDerivation has been deprecated, please use stdenv.mkDerivation
+        directly. You can migrate by adding `pkg-config`, `xfce4-dev-tools`, and
+        `wrapGAppsHook3` to your nativeBuildInputs and `--enable-maintainer-mode`
+        to your configureFlags.
+      '' (callPackage ./mkXfceDerivation.nix { }); # added 2025-12-22
+
       xinitrc = self.xfce4-session.xinitrc; # added 2019-11-04
 
       thunar-bare = self.thunar-unwrapped; # added 2019-11-04