anchor.diff:  assert traySupport         -> gnome2 != null;
   assert pgpSupport          -> gpgme != null;
   assert pythonPluginSupport -> python != null;
  +assert omemoSupport        -> libsignal-protocol-c != null && libgcrypt != null;
   
   with stdenv.lib;
   
  
positive.code: , traySupport ? true,           gnome2 ? null
  , pgpSupport ? true,            gpgme ? null
  , pythonPluginSupport ? true,   python ? null
  }:
  
  assert autoAwaySupport     -> libXScrnSaver != null && libX11 != null;
  
negative.code:     ++ optionals notifySupport       [ libnotify gdk-pixbuf ]
      ++ optionals traySupport         [ gnome2.gtk ]
      ++ optionals pgpSupport          [ gpgme ]
      ++ optionals pythonPluginSupport [ python ]
      ++ optionals omemoSupport        [ libsignal-protocol-c libgcrypt ];
  
    # Enable feature flags, so that build fail if libs are missing
    configureFlags = [ "--enable-c-plugins" "--enable-otr" ]
      ++ optionals notifySupport       [ "--enable-notifications" ]
      ++ optionals traySupport         [ "--enable-icons" ]
      ++ optionals pgpSupport          [ "--enable-pgp" ]
      ++ optionals pythonPluginSupport [ "--enable-python-plugins" ]
      ++ optionals omemoSupport        [ "--enable-omemo" ];
  
    preAutoreconf = ''
      mkdir m4
  