require fixed protobuf -DGOOGLE_PROTOBUF_NO_RTTI build. thx lmasko for spotting this

http://lists.pld-linux.org/mailman/pipermail/pld-devel-en/2014-August/024008.html
https://groups.google.com/a/chromium.org/forum/#!topic/chromium-packagers/i-wFQoivG1k