There's a UI in qml/customexec/cmake/qmake run configs for choosing the
debugger languages (C++ and QML). The default for all except .qmlproject
is only C++, so default debugging behavior is the same. However, if the
user wants to do simultaneous debugging with two languages, or only
debug QML, they can select the languages from Run Settings and it will
be remembered.

Reviewed-by: hunger