Qt Speech Voice Selection does not work on macOS

On macOS, Qt Speech voice selection does not work.

• QTextToSpeech::availableVoices() returns the correct voices for a corresponding locale. This is expected behaviour.
• However, when QTextToSpeech::setVoice() is called with a voice from the list available voices, the function has no effect. The text-to-speech engine will not update to the new voice.

Using the hello speak example, see attached video. Console log output indicates that available voices is called and returns the expected list of voices for each locale (Cantonese, Mandarin/China, Mandarin/Taiwan. However, the voice that "speaks" is always Sinji, which is the voice for Cantonese.