gnulib: Fix path to perl in prefix-gnulib-mk

{ lib, stdenv, fetchFromSavannah, python3 }:

{ lib, stdenv, fetchFromSavannah, python3, perl }:

stdenv.mkDerivation rec {

  pname = "gnulib";

  postPatch = ''

    patchShebangs gnulib-tool.py

    substituteInPlace build-aux/{prefix-gnulib-mk,useless-if-before-free,update-copyright,gitlog-to-changelog,announce-gen} \

    --replace-fail 'exec perl' 'exec ${lib.getExe perl}'

  '';

  buildInputs = [ python3 ];