Globally disable WindowContextHelpButtonHint

Do set the global application flag AA_DisableWindowContextHelpButton
to avoid having to unset the default WindowContextHelpButtonHint
in every single dialog.

AA_DisableWindowContextHelpButton was added in Qt 5.10.

Change-Id: I21fe8bc5ddfa4c01ec7a799b04bfb6ff1c9d6d86
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/app/main.cpp

@@ -546,6 +546,7 @@ int main(int argc, char **argv)
 #endif
 
     app.setAttribute(Qt::AA_UseHighDpiPixmaps);
+    app.setAttribute(Qt::AA_DisableWindowContextHelpButton);
 
     PluginManager pluginManager;
     PluginManager::setPluginIID(QLatin1String("org.qt-project.Qt.QtCreatorPlugin"));