wxGTK31: drop mesa on darwin

pkgs/development/libraries/wxwidgets/wxGTK31.nix

···
 { lib
 , stdenv
 , fetchFromGitHub
-, fetchurl
-, gnome2
 , gst_all_1
 , gtk3
 , libGL
···
 , compat30 ? true
 , unicode ? true
 , withEGL ? true
-, withMesa ? lib.elem stdenv.hostPlatform.system lib.platforms.mesaPlatforms
+, withMesa ? !stdenv.isDarwin
 , withWebKit ? stdenv.isDarwin
 , webkitgtk
 , setfile
···
     "--enable-webviewwebkit"
   ];
 
-  SEARCH_LIB = "${libGLU.out}/lib ${libGL.out}/lib ";
+  SEARCH_LIB = lib.optionalString (!stdenv.isDarwin) "${libGLU.out}/lib ${libGL.out}/lib ";
 
   preConfigure = ''
     substituteInPlace configure --replace \