anchor.diff:  { fetchurl, stdenv, sqlite, pkgconfig, autoreconfHook
   , xapian, glib, gmime, texinfo , emacs, guile
  -, gtk3, webkitgtk24x, libsoup, icu }:
  +, gtk3, webkitgtk24x, libsoup, icu
  +, withMug ? stdenv.isLinux }:
   
   stdenv.mkDerivation rec {
     version = "0.9.18";
  
positive.code:   '';
  
    # Install mug and msg2pdf
    postInstall = ''
      cp -v toys/msg2pdf/msg2pdf $out/bin/
      cp -v toys/mug/mug $out/bin/
    '';
  
negative.code: 
    buildInputs = [
      sqlite pkgconfig xapian glib gmime texinfo emacs guile libsoup icu
      autoreconfHook ] ++ stdenv.lib.optionals withMug [ gtk3 webkitgtk24x ];
  
    preBuild = ''
      # Fix mu4e-builddir (set it to $out)
  