anchor.diff:    outputs = [ "out" "doc" ];
     outputMan = "out"; # users will want `man man` to work
   
  -  nativeBuildInputs = [ pkgconfig makeWrapper ];
  -  buildInputs = [ libpipeline db groff ];
  +  nativeBuildInputs = [ pkgconfig makeWrapper groff ]
  +    ++ stdenv.lib.optionals doCheck checkInputs;
  +  buildInputs = [ libpipeline db groff ]; # (Yes, 'groff' is both native and build input)
  +  checkInputs = [ libiconv /* for 'iconv' binary */ ];
   
     postPatch = ''
       substituteInPlace src/man_db.conf.in \
  
positive.code: { stdenv, fetchurl, pkgconfig, libpipeline, db, groff, makeWrapper }:
  
  stdenv.mkDerivation rec {
    name = "man-db-2.7.5";
  
negative.code:     done
    '';
  
    postFixup = stdenv.lib.optionalString (buildPackages.groff != groff) ''
      # Check to make sure none of the outputs depend on build-time-only groff:
      for outName in $outputs; do
        out=''${!outName}
        echo "Checking $outName(=$out) for references to build-time groff..."
        if grep -r '${buildPackages.groff}' $out; then
          echo "Found an erroneous dependency on groff ^^^" >&2
          exit 1
        fi
      done
    '';
  
    enableParallelBuilding = true;
  
    doCheck = true;
  