anchor.diff:  
     postPatch = ''
       sed -ie '/sys\/sysctl.h/d' source/Irrlicht/COSOperator.cpp
  +  '' + lib.optionalString stdenv.isAarch64 ''
  +    substituteInPlace source/Irrlicht/Makefile \
  +      --replace "-DIRRLICHT_EXPORTS=1" "-DIRRLICHT_EXPORTS=1 -DPNG_ARM_NEON_OPT=0"
     '';
   
     preConfigure = ''
  
positive.code: { lib, stdenv, fetchzip, libGLU, libGL, libXrandr, libX11, libXxf86vm }:
  
  let
    common = import ./common.nix { inherit fetchzip; };
  
negative.code:     mkdir -p $out/lib
    '';
  
    buildInputs = [ libGLU libGL libXrandr libX11 libXxf86vm ]
                  ++ lib.optional stdenv.isAarch64 zlib;
  
    meta = {
      homepage = "http://irrlicht.sourceforge.net/";
  