QMetaType: unlock QReadLocker early

Unlock the QReadLocker after we're done with the registry, before we
perform expensive operations such as I/O and QByteArrayList::join().

Pick-to: 6.3
Change-Id: I96549c517a2b4ffe34a70ea83f8c061ff9620795
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qmetatype.cpp

@@ -207,6 +207,7 @@ const char *QtMetaTypePrivate::typedefNameForType(const QtPrivate::QMetaTypeInte
         if (it.value() == type_d && it.key() != officialName)
             otherNames << it.key();
     }
+    l.unlock();
     if (!otherNames.isEmpty())
         qWarning("QMetaType: type %s has more than one typedef alias: %s, %s",
                  type_d->name, name, otherNames.join(", ").constData());