Build: Set missing override as error

I couldn't find a similar flag for MSVC

plugins/Assimp/Plugin.cpp

@@ -918,7 +918,7 @@ namespace
 				meshLoader.UnregisterLoader(m_meshLoaderEntry);
 			}
 
-			std::string_view GetDescription() const
+			std::string_view GetDescription() const override
 			{
 				return "Adds supports to load meshes and animations using Assimp";
 			}
@@ -963,4 +963,4 @@ extern "C"
 		return plugin.release();
 	}
 }
-#endif
+#endif