add an additional check to ensure that the libtorrent folder has files in it

setup.py

@@ -213,7 +213,7 @@ except ImportError:
 else:
     build_libtorrent = False
 
-if build_libtorrent and os.path.exists("libtorrent"):
+if build_libtorrent and os.path.exists("libtorrent") and os.listdir("libtorrent"):
     # There isn't a system libtorrent library, so let's build the one included with deluge
     libtorrent = Extension(
         'libtorrent',