anchor.diff:  , libx11
   , libxcb
   , lzo
  -, mesa_noglu
  +, opengl-dummy
   , xorg
   , zlib
   
  
positive.code: let
    inherit (lib)
      boolEn
      optionalString;
  in
  stdenv.mkDerivation rec {
  
negative.code:     "--enable-interpreter"
      "--disable-symbol-lookup"
      #"--enable-some-floating-point"
      "--${boolwt opengl-dummy.glx}-x"
      #(wtFlag "skia" true "yes")
      #(wtFlag "skia-build-type" true "Release")
      "--without-gallium"
  