Utils: Explicitly include export macro in PersistentSettings

Change-Id: I6734da09919df0669e7715cd362455d6e21cb04b
Reviewed-by: Jochen Becher <jochen_becher@gmx.de>
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/libs/utils/persistentsettings.h

@@ -26,6 +26,7 @@
 #pragma once
 
 #include "fileutils.h"
+#include "utils_global.h"
 
 #include <QVariant>