xfce.exo: Move perl to nativeBuildInputs

* exo-compose-mail has been removed (both here and xfce4-settings).
* Xfce is actively getting rid of intltool and to get ready for it,
  make-exo-alias.pl requires perl.

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

@@ -1,5 +1,14 @@
-{ lib, mkXfceDerivation, docbook_xsl, glib, libxslt, gtk3
-, libxfce4ui, libxfce4util, perl }:
+{
+  lib,
+  mkXfceDerivation,
+  docbook_xsl,
+  glib,
+  libxslt,
+  gtk3,
+  libxfce4ui,
+  libxfce4util,
+  perl,
+}:
 
 mkXfceDerivation {
   category = "xfce";
@@ -11,6 +20,7 @@ mkXfceDerivation {
   nativeBuildInputs = [
     libxslt
     docbook_xsl
+    perl
   ];
 
   buildInputs = [
@@ -18,7 +28,6 @@ mkXfceDerivation {
     glib
     libxfce4ui
     libxfce4util
-    (perl.withPackages(ps: with ps; [ URI ])) # for $out/lib/xfce4/exo/exo-compose-mail
   ];
 
   meta = with lib; {