CMake: Mark configuration items that were taken from the CMakeCache.txt file

Change-Id: Id9e707d7b07d35ade44959955db61810e34f7b30
Reviewed-by: Tim Jenssen <tim.jenssen@qt.io>

src/plugins/cmakeprojectmanager/configmodel.h

@@ -46,6 +46,7 @@ public:
         QString key;
         Type type = STRING;
         bool isAdvanced = false;
+        bool inCMakeCache = false;
         QString value;
         QString description;
         QStringList values;