CoreAudio: Fix iphone build after audio device refactor (#17742)

drivers/coreaudio/audio_driver_coreaudio.h

@@ -56,9 +56,11 @@ class AudioDriverCoreAudio : public AudioDriver {
 
 	Vector<int32_t> samples_in;
 
+#ifdef OSX_ENABLED
 	static OSStatus output_device_address_cb(AudioObjectID inObjectID,
 			UInt32 inNumberAddresses, const AudioObjectPropertyAddress *inAddresses,
 			void *inClientData);
+#endif
 
 	static OSStatus output_callback(void *inRefCon,
 			AudioUnitRenderActionFlags *ioActionFlags,