anchor.diff:  
   let
     inherit (lib) optional optionals optionalAttrs optionalString;
  -  wxPackages2 = if stdenv.isDarwin then [ wxmac ] else wxPackages;
  +  wxPackages2 = if stdenv.isDarwin then [ wxGTK ] else wxPackages;
   
   in
   stdenv.mkDerivation ({
  
positive.code: }:
  
  assert wxSupport -> (if stdenv.isDarwin
  then wxmac != null
  else libGL != null && libGLU != null && wxGTK != null && xorg != null);
  
  assert odbcSupport -> unixODBC != null;
  
negative.code: , libGL ? null
  , libGLU ? null
  , wxGTK ? null
  , xorg ? null
  , parallelBuild ? false
  , systemd
  