anchor.diff:    nativeBuildInputs = [ autoreconfHook pkg-config ];
     propagatedBuildInputs = [ zlib ]
       ++ lib.optional mpiSupport mpi
  -    ++ lib.optional (mpiSupport && mpi == openmpi) openssh
  +    ++ lib.optional isOpenmpi openssh
     ;
     inherit debugEnable mpiSupport;
   
  
positive.code:     ${if mpiSupport then "unset CC" else ""}
    '';
  
    configureFlags = lib.optional debugEnable "--enable-debug"
      ++ lib.optional mpiSupport "--enable-mpi"
    ;
  
    makeFlags = [ "V=0" ];
  
    dontDisableStatic = true;
    enableParallelBuilding = true;
    doCheck = stdenv.hostPlatform == stdenv.buildPlatform;
  
    meta = {
      branch = "prev3-develop";
  
negative.code: { lib, stdenv, fetchFromGitHub
  , autoreconfHook, pkg-config
  , p4est-sc-debugEnable ? true, p4est-sc-mpiSupport ? true
  , mpi, openssh, zlib
  }:
  
  let
    dbg = if debugEnable then "-dbg" else "";
    debugEnable = p4est-sc-debugEnable;
    mpiSupport = p4est-sc-mpiSupport;
    isOpenmpi = mpiSupport && mpi.pname == "openmpi";
  in
  stdenv.mkDerivation {
    pname = "p4est-sc${dbg}";
  