Autogen: Recognize the new Q_NAMESPACE_EXPORT macro in AUTOMOC

Qt 5.14 introduced a new moc keyword `Q_NAMESPACE_EXPORT`.

Qt-Issue: https://bugreports.qt.io/browse/QTBUG-68014

Modules/CMakeGenericSystem.cmake

@@ -27,7 +27,7 @@ set(CMAKE_FIND_LIBRARY_SUFFIXES ".so" ".a")
 set(CMAKE_AUTOGEN_ORIGIN_DEPENDS ON)
 set(CMAKE_AUTOMOC_COMPILER_PREDEFINES ON)
 set(CMAKE_AUTOMOC_PATH_PREFIX ON)
-set(CMAKE_AUTOMOC_MACRO_NAMES "Q_OBJECT" "Q_GADGET" "Q_NAMESPACE")
+set(CMAKE_AUTOMOC_MACRO_NAMES "Q_OBJECT" "Q_GADGET" "Q_NAMESPACE" "Q_NAMESPACE_EXPORT")
 
 # basically all general purpose OSs support shared libs
 set_property(GLOBAL PROPERTY TARGET_SUPPORTS_SHARED_LIBS TRUE)