anchor.diff:  
   let
     inherit (lib)
  -    boolEn
  -    boolString
  -    boolWt;
  +    concatStringsSep
  +    optionals;
  +
  +  gl_platforms = [ ]
  +    ++ optionals opengl-dummy.glx [
  +      "glx"
  +    ] ++ optionals opengl-dummy.egl [
  +      "egl"
  +    ];
   
     sources = {
       "1.12" = {
  
positive.code: { stdenv
  , fetchurl
  , lib
  , python3
  
  , bzip2
  
negative.code:   };
  
    nativeBuildInputs = [
      meson
      ninja
      python3
    ];
  
  