C++: update project info once after finishing adding all project parts.

So that recalculating the information is not O(n^2) but linear.

Change-Id: I69903e0b5ad321d071804d782ad634a3f300e71a
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/genericprojectmanager/genericproject.cpp

@@ -346,6 +346,7 @@ void GenericProject::refreshCppCodeModel()
     foreach (Core::Id language, languages)
         setProjectLanguage(language, true);
 
+    pInfo.finish();
     m_codeModelFuture = modelManager->updateProjectInfo(pInfo);
 }