gqrx: use qt5's mkDerivation

Fixes

  qt.qpa.plugin: Could not find the Qt platform plugin "xcb" in ""
  This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

See NixOS#65399

pkgs/applications/radio/gqrx/default.nix

@@ -1,12 +1,13 @@
 { stdenv, fetchFromGitHub, cmake, qtbase, qtsvg, gnuradio, boost, gr-osmosdr
+, mkDerivation
 # drivers (optional):
 , rtl-sdr, hackrf
 , pulseaudioSupport ? true, libpulseaudio
 }:
 
 assert pulseaudioSupport -> libpulseaudio != null;
 
-stdenv.mkDerivation rec {
+mkDerivation rec {
   name = "gqrx-${version}";
   version = "2.11.5";