CMakeProject: Prefer assignment to out parameter

Also change method names from update...() to create...() and mark as
const. This communicates that the objects the methods are called on are
neither altered nor updated.

Change-Id: I29e84dc398ded3ffcbf90741227362c6b4be2bf9
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>

src/plugins/cmakeprojectmanager/builddirreader.h

@@ -67,7 +67,7 @@ public:
     virtual CMakeConfig takeParsedConfiguration() = 0;
     virtual void generateProjectTree(CMakeProjectNode *root,
                                      const QList<const ProjectExplorer::FileNode *> &allFiles) = 0;
-    virtual void updateCodeModel(CppTools::RawProjectParts &rpps) = 0;
+    virtual CppTools::RawProjectParts createRawProjectParts() const = 0;
 
 signals:
     void isReadyNow() const;