anchor.diff:  , withGui ? false, gtk2 ? null, withTeensyduino ? false
     /* Packages needed for Teensyduino */
   , upx, fontconfig, xorg, gcc
  -, atk, glib, pango, gdk-pixbuf, libpng12, expat, freetype,
  +, atk, glib, pango, gdk-pixbuf, libpng12, expat, freetype
  +, cairo, udev
   }:
   
   assert withGui -> gtk2 != null;
  
positive.code: 
    teensy_libpath = stdenv.lib.makeLibraryPath [
      atk
      expat
      fontconfig
      freetype
  
negative.code:     libpng12
      libusb
      pango
      udev
      xorg.libSM
      xorg.libX11
      xorg.libXext
      xorg.libXft
      xorg.libXinerama
      xorg.libXxf86vm
      zlib
    ];
    teensy_architecture =
  