xdg-utils: add patch which adds NIXOS_XDG_OPEN_USE_PORTAL env var

from https://github.com/freedesktop/xdg-utils/pull/12

pkgs/tools/X11/xdg-utils/allow-forcing-portal-use.patch

···
+From 835eed6a2b975fba40c3ac18b4cf5429ba9d2836 Mon Sep 17 00:00:00 2001
+From: Luna Nova <[e-mail]>
+Date: Wed, 7 Sep 2022 08:45:56 -0700
+Subject: [PATCH] xdg-open: add $XDG_OPEN_USE_PORTAL env var
+
+When set, the same mechanism that is used in a flatpak is used,
+a dbus call to the portal. This is useful for distros with non-flatpak
+wrapper or sandboxing features which require the same treatment, eg NixOS.
+
+See https://github.com/NixOS/nixpkgs/issues/160923
+---
+ scripts/xdg-open.in | 4 ++++
+ 1 file changed, 4 insertions(+)
+
+diff --git a/scripts/xdg-open.in b/scripts/xdg-open.in
+index 8de839a..80d8fb3 100644
+--- a/scripts/xdg-open.in
++++ b/scripts/xdg-open.in
+@@ -508,6 +508,10 @@ if [ x"$DE" = x"" ]; then
+     DE=generic
+ fi
+ 
++if [ -n "$NIXOS_XDG_OPEN_USE_PORTAL"  ]; then
++    DE=flatpak
++fi
++
+ DEBUG 2 "Selected DE $DE"
+ 
+ # sanitize BROWSER (avoid calling ourselves in particular)

pkgs/tools/X11/xdg-utils/default.nix

···
 { lib, stdenv, fetchFromGitLab, fetchFromGitHub
 , file, libxslt, docbook_xml_dtd_412, docbook_xsl, xmlto
 , w3m, gnugrep, gnused, coreutils, xset, perlPackages
-, mimiSupport ? false, gawk }:
+, mimiSupport ? false, gawk
+, withXdgOpenUsePortalPatch ? true }:
 
 let
   # A much better xdg-open
···
     rev = "d11b33ec7f24cfb1546f6b459611d440013bdc72";
     sha256 = "sha256-8PtXfI8hRneEpnUvIV3M+6ACjlkx0w/NEiJFdGbbHnQ=";
   };
+
+  patches = lib.optionals withXdgOpenUsePortalPatch [
+    # Allow forcing the use of XDG portals using NIXOS_XDG_OPEN_USE_PORTAL environment variable.
+    # Upstream PR: https://github.com/freedesktop/xdg-utils/pull/12
+    ./allow-forcing-portal-use.patch
+  ];
 
   # just needed when built from git
   nativeBuildInputs = [ libxslt docbook_xml_dtd_412 docbook_xsl xmlto w3m ];