anchor.diff:  
     buildInputs = [
       autoconf libtool automake libsodium ncurses libopus
  -    libvpx libconfig pkgconfig
  +    libvpx check libconfig pkgconfig
     ];
   
     doCheck = true;
  
positive.code:     sha256 = "1rsh1pbwvngsx5slmd6608b1zqs3jvq70bjr9zyziap9vxka3z1v";
    };
  
    preConfigure = ''
      autoreconf -i
    '';
  
negative.code: { stdenv, fetchurl, autoconf, libtool, automake, libsodium, ncurses, libopus
  , libvpx, check, libconfig, pkgconfig }:
  
  let
    version = "e1158be5a6";
  