Debugging shouldn't continue if there's a build error

[sean-mcmanus]

With the cppbuild task, add a build error and do F5 or the Build/Run button.

Ideally, it would not continue to the debug/run stages if a build error occurred. Not sure if that's possible.

In particular, the build error in the Terminal gets covered up when it switches to the Debug Console pane, so it's easy to miss.