qbittorrent: add gui & webui optionals

pkgs/applications/networking/p2p/qbittorrent/default.nix

@@ -1,31 +1,42 @@
-{ stdenv, fetchurl, qt4, which, dbus_libs, boost, libtorrentRasterbar
-, pkgconfig }:
+{ stdenv, fetchurl, pkgconfig, which
+, boost, libtorrentRasterbar, qt4
+, debugSupport ? false # Debugging
+, guiSupport ? true, dbus_libs ? null # GUI (disable to run headless)
+, webuiSupport ? true # WebUI
+}:
 
+assert guiSupport -> (dbus_libs != null);
+
+with stdenv.lib;
 stdenv.mkDerivation rec {
-  name = "qbittorrent-3.1.11";
+  name = "qbittorrent-${version}";
+  version = "3.1.11";
 
   src = fetchurl {
     url = "mirror://sourceforge/qbittorrent/${name}.tar.xz";
     sha256 = "0qvz8ifk01b9sw9x5yh3b5kmssx5yi026zvgvabdvfaqkvcmw43i";
   };
 
-  buildInputs = [
-    qt4 which dbus_libs boost libtorrentRasterbar pkgconfig
-  ];
+  nativeBuildInputs = [ pkgconfig which ];
+
+  buildInputs = [ boost libtorrentRasterbar qt4 ]
+    ++ optional guiSupport dbus_libs;
 
   configureFlags = [
     "--with-libboost-lib=${boost.lib}/lib"
     "--with-libboost-inc=${boost.dev}/include"
-  ];
+    (if guiSupport then "" else "--disable-gui")
+    (if webuiSupport then "" else "--disable-webui")
+  ] ++ optional debugSupport "--enable-debug";
 
   # https://github.com/qbittorrent/qBittorrent/issues/1992 
-  #enableParallelBuilding = true;
+  enableParallelBuilding = false;
 
-  meta = with stdenv.lib; {
+  meta = {
     description = "Free Software alternative to µtorrent";
-    homepage = http://www.qbittorrent.org/;
-    license = licenses.gpl2;
+    homepage    = http://www.qbittorrent.org/;
+    license     = licenses.gpl2;
     maintainers = with maintainers; [ viric ];
-    platforms = platforms.linux;
+    platforms   = platforms.linux;
   };
 }