Fix Windows build without features.filesytemiterator

Task-number: QTBUG-61671
Change-Id: I65a96ca51efee303602c836e5b0177b1a63d1a7a
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@qt.io>

src/corelib/io/io.pri

@@ -113,7 +113,10 @@ win32 {
         SOURCES += io/qfilesystemwatcher_win.cpp
         HEADERS += io/qfilesystemwatcher_win_p.h
         SOURCES += io/qfilesystemengine_win.cpp
-        SOURCES += io/qfilesystemiterator_win.cpp
+
+        qtConfig(filesystemiterator) {
+            SOURCES += io/qfilesystemiterator_win.cpp
+        }
 
     !winrt {
         HEADERS += \