QCocoaEventDispatcher: Save interrupt state between embedded calls

Since QCocoaEventDispatcher::processEvents() resets the interrupt
state, this may prevent a higher level event loop from returning.

For example, calling QMenu::exec() and, as a result of an action
being triggered, the application calls QCoreApplication::processEvents()
after QMenu::hideEvent(). In this case, the menu event loop can be
stuck until we run another event loop.

Task-number: QTBUG-53947
Change-Id: If7efe1c3c07f7222c695195cbb4f41715e49b02e
Reviewed-by: Timur Pocheptsov <timur.pocheptsov@theqtcompany.com>
Reviewed-by: Wayne Arnold <wayne.arnold@autodesk.com>
Reviewed-by: Morten Johan Sørvig <morten.sorvig@qt.io>

src/plugins/platforms/cocoa/qcocoaeventdispatcher.mm

@@ -342,7 +342,7 @@ static inline void qt_mac_waitForMoreEvents(NSString *runLoopMode = NSDefaultRun
 bool QCocoaEventDispatcher::processEvents(QEventLoop::ProcessEventsFlags flags)
 {
     Q_D(QCocoaEventDispatcher);
-    d->interrupt = false;
+    QBoolBlocker interruptBlocker(d->interrupt, false);
 
     bool interruptLater = false;
     QtCocoaInterruptDispatcher::cancelInterruptLater();