ClangCodeModel: Provide diagnostics via clangd

Change-Id: Ib45a62ebe200c2b56a1bb1a66f8a92103e60d092
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangdiagnosticmanager.h

@@ -66,6 +66,8 @@ public:
     static void clearTaskHubIssues();
     void generateTaskHubIssues();
 
+    static void addTask(const ClangBackEnd::DiagnosticContainer &diagnostic, bool isChild = false);
+
 private:
     void cleanMarks();
     QString filePath() const;