suil: remove qt4 support

pkgs/development/libraries/audio/suil/default.nix

···
 { stdenv, lib, fetchurl, gtk2, lv2, pkg-config, python3, serd, sord, sratom
 , wafHook
-, withQt4 ? true, qt4 ? null
-, withQt5 ? false, qt5 ? null }:
-
-# I haven't found an XOR operator in nix...
-assert withQt4 || withQt5;
-assert !(withQt4 && withQt5);
+, withQt5 ? true, qt5 ? null
+}:
 
 stdenv.mkDerivation rec {
   pname = "suil";
   version = "0.10.6";
-  name = "${pname}-qt${if withQt4 then "4" else "5"}-${version}";
 
   src = fetchurl {
     url = "https://download.drobilla.net/${pname}-${version}.tar.bz2";
···
 
   nativeBuildInputs = [ pkg-config wafHook python3 ];
   buildInputs = [ gtk2 lv2 serd sord sratom ]
-    ++ (lib.optionals withQt4 [ qt4 ])
-    ++ (lib.optionals withQt5 (with qt5; [ qtbase qttools ]));
+    ++ lib.optionals withQt5 (with qt5; [ qtbase qttools ]);
 
   dontWrapQtApps = true;
 

pkgs/top-level/all-packages.nix

···
 
   suil = callPackage ../development/libraries/audio/suil { };
 
-  suil-qt5 = suil.override {
-    withQt4 = false;
-    withQt5 = true;
-  };
-  suil-qt4 = suil.override {
-    withQt4 = true;
-    withQt5 = false;
-  };
-
   sundials = callPackage ../development/libraries/sundials {
     python = python3;
   };
···
 
   audacity = callPackage ../applications/audio/audacity {
     inherit (darwin.apple_sdk.frameworks) AppKit AudioToolbox AudioUnit Carbon CoreAudio CoreAudioKit CoreServices;
-    suil = suil-qt5;
   };
 
   audio-recorder = callPackage ../applications/audio/audio-recorder { };