ckb-next: Fix udev rule

The current udev rule uses `/usr/bin/env sed`, which will fail the build
if the package is added to `services.udev.packages`

pkgs/tools/misc/ckb-next/default.nix

@@ -1,5 +1,5 @@
 { lib, wrapQtAppsHook, fetchFromGitHub, substituteAll, udev, stdenv
-, pkg-config, qtbase, cmake, zlib, kmod, libXdmcp, qttools, qtx11extras, libdbusmenu
+, pkg-config, qtbase, cmake, zlib, kmod, libXdmcp, qttools, qtx11extras, libdbusmenu, gnused
 , withPulseaudio ? stdenv.isLinux, libpulseaudio, quazip
 }:
 
@@ -47,6 +47,11 @@ stdenv.mkDerivation rec {
     })
   ];
 
+  postInstall = ''
+    substituteInPlace "$out/lib/udev/rules.d/99-ckb-next-daemon.rules" \
+      --replace-fail "/usr/bin/env sed" "${lib.getExe gnused}"
+  '';
+
   meta = with lib; {
     description = "Driver and configuration tool for Corsair keyboards and mice";
     homepage = "https://github.com/ckb-next/ckb-next";