Replace Q_OS_OSX with Q_OS_MACOS

Change-Id: Ibee0c259d7df86a8df58b1ad12549b145f715397
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>

src/plugins/coreplugin/windowsupport.cpp

@@ -146,7 +146,7 @@ WindowList::~WindowList()
 
 void WindowList::addWindow(QWidget *window)
 {
-#ifdef Q_OS_OSX
+#ifdef Q_OS_MACOS
     if (!m_dockMenu) {
         m_dockMenu = new QMenu;
         m_dockMenu->setAsDockMenu();