ClangCodeModel: Fix re-parsing with new options

If the command line options changed unload the unit so the next
SemanticMarker::reparse() will call clang_parseTranslationUnit() with
the new options.

Task-number: QTCREATORBUG-11606
Change-Id: I44e3da97850abd875a88abde0b406b14198b5be8
Reviewed-by: Eike Ziller <eike.ziller@theqtcompany.com>
Reviewed-by: Erik Verbruggen <erik.verbruggen@theqtcompany.com>

src/plugins/clangcodemodel/semanticmarker.cpp

@@ -83,6 +83,7 @@ void SemanticMarker::setCompilationOptions(const QStringList &options)
         return;
 
     m_unit->setCompilationOptions(options);
+    m_unit->unload();
 }
 
 void SemanticMarker::reparse(const UnsavedFiles &unsavedFiles)