Expression to create /run/opengl-driver environment

with import <nixpkgs> {};

let
   nvidiaVersion = stdenv.mkDerivation {
     name = "nvidia-version";
     src = /usr/share/doc/nvidia;
     installPhase = ''
        VERSION=$(/usr/bin/nvidia-settings -v | sed -ne 's/^.*version \([0-9]\+\.[0-9]\+\).*/\1/p')
        echo -n $VERSION > $out
     '';
   };
   nvidia_hashes = {
      "375.20" = "02v20xns8w4flpllibc684g5yghi5dy28avsarccjyn5knhl03ni";
   };
   versionNumber = stdenv.lib.readFile "${nvidiaVersion}";
   nvidia_support = stdenv.lib.overrideDerivation
      linuxPackages.nvidia_x11 (old: rec {
         name = "nvidia-x11-${versionNumber}";
         src = fetchurl {
            url = "http://download.nvidia.com/XFree86/Linux-x86_64/${versionNumber}/NVIDIA-Linux-x86_64-${versionNumber}.run";
            sha256 = nvidia_hashes.${versionNumber};
         };
      });
in buildEnv {
  name = "opengl-driver";
  paths = [ nvidia_support mesa mesa_noglu ];
}