anchor.diff:    outputs = [ "out" "dev" "bin" ];
   
     nativeBuildInputs = [ pkgconfig meson ninja ];
  -  buildInputs = [ libpthreadstubs libpciaccess valgrind-light ];
  +  buildInputs = [ libpthreadstubs libpciaccess ]
  +    ++ lib.optional withValgrind valgrind-light;
   
     patches = [ ./cross-build-nm-path.patch ];
   
  
positive.code:     homepage = https://dri.freedesktop.org/libdrm/;
      description = "Library for accessing the kernel's Direct Rendering Manager";
      license = "bsd";
      platforms = stdenv.lib.platforms.unix;
    };
  }
  
negative.code: { stdenv, lib, fetchurl, pkgconfig, meson, ninja, libpthreadstubs, libpciaccess
  , withValgrind ? valgrind-light.meta.available, valgrind-light
  }:
  
  stdenv.mkDerivation rec {
    pname = "libdrm";
  