QTBUG-58461 , we found on rhel72(which is used in Linux packaging), speech-dispatcher 0.7.1 was installed, but missing pkg-config file for it, which is needed by qtspeech module.
speech-dispatcher.pc.0.7.1 is a home made version.
speech-dispatcher.pc.0.8.3 is from ubuntu.
One solution is that put speech-dispatcher.pc.0.7.1 in correct place on rhel 7.2.
Another better solution is that upgrade speech-dispatcher to 0.8.3, and make sure pkg-config is included, either from upstream package or from our own.