xfce.exo: Move away from mkXfceDerivation

To reduce the diff when build system change comes.
mkXfceDerivation is generally pointless with meson.

pkgs/desktops/xfce/core/exo/default.nix

@@ -1,26 +1,46 @@
 {
+  stdenv,
   lib,
-  mkXfceDerivation,
+  fetchFromGitLab,
   docbook_xsl,
+  gettext,
+  pkg-config,
+  xfce4-dev-tools,
+  wrapGAppsHook3,
   glib,
   libxslt,
   gtk3,
   libxfce4ui,
   libxfce4util,
   perl,
+  gitUpdater,
 }:
 
-mkXfceDerivation {
-  category = "xfce";
+stdenv.mkDerivation (finalAttrs: {
   pname = "exo";
   version = "4.20.0";
 
-  sha256 = "sha256-mlGsFaKy96eEAYgYYqtEI4naq5ZSEe3V7nsWGAEucn0=";
+  outputs = [
+    "out"
+    "dev"
+  ];
+
+  src = fetchFromGitLab {
+    domain = "gitlab.xfce.org";
+    owner = "xfce";
+    repo = "exo";
+    tag = "exo-${finalAttrs.version}";
+    hash = "sha256-mlGsFaKy96eEAYgYYqtEI4naq5ZSEe3V7nsWGAEucn0=";
+  };
 
   nativeBuildInputs = [
     libxslt
     docbook_xsl
+    gettext
     perl
+    pkg-config
+    xfce4-dev-tools
+    wrapGAppsHook3
   ];
 
   buildInputs = [
@@ -30,8 +50,19 @@ mkXfceDerivation {
     libxfce4util
   ];
 
+  configureFlags = [ "--enable-maintainer-mode" ];
+  enableParallelBuilding = true;
+
+  passthru.updateScript = gitUpdater {
+    rev-prefix = "exo-";
+    odd-unstable = true;
+  };
+
   meta = {
     description = "Application library for Xfce";
+    homepage = "https://gitlab.xfce.org/xfce/exo";
+    license = lib.licenses.gpl2Plus;
+    platforms = lib.platforms.linux;
     teams = [ lib.teams.xfce ];
   };
-}
+})