Fix system tray icon on macOS
Simply add Resources/icons into theme search path.
According to:
When icon themes are installed in a suitable (system) location, applications can be built and deployed as on Linux/BSD provided that the location is registered by calling QIcon::setThemeSearchPath(). This can be done early in the main() function, or in a plugin that Qt loads automatically when the application starts up (a platform theme plugin, for instance). The more usual deployment strategy on those platforms consists of creating standalone applications where each has its own copy of all dependencies and required resources.
Edited by Weixuan Xiao