Add Q_FLAG for QEventLoop::ProcessEventsFlags

Helps debugging when printing the flags.

Pick-to: 6.3 6.2
Change-Id: Icb306bb1efaf9d3c645c2ac86796d95da5afc4a3
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/kernel/qeventloop.h

@@ -66,6 +66,7 @@ public:
         ApplicationExec = 0x80,
     };
     Q_DECLARE_FLAGS(ProcessEventsFlags, ProcessEventsFlag)
+    Q_FLAG(ProcessEventsFlags)
 
     bool processEvents(ProcessEventsFlags flags = AllEvents);
     void processEvents(ProcessEventsFlags flags, int maximumTime);