Enable QML debugging only if project includes a qml library

Use the same check as in the DebuggerRunConfigurationAspect to
decide whether to  enable qml debugging, or not. This allows
us to follow the qmakestep setting in the run settings in a
follow-up change.

Task-number: QTCREATORBUG-11474
Change-Id: I67900cf719a56c0246e792c6aca66ce8e5d77daf
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>
Update debugger language aspect in run settings when qmake step changes

When QML language debugging hasn't been set to a fixed state yet by the
user try to find a qmake step to decide whether to enable QML debugging by default
or not.

This is a hack, breaking the separation between qt build steps and debugger
run settings. However, adding a generic project infrastructure for this specific
use case is probably overkill...

Task-number: QTCREATORBUG-11474
Change-Id: Ib65c8474b9b7ec187769c209531ff56bc8293cde
Reviewed-by: Aurindam Jana <aurindam.jana@digia.com>
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Reviewed-by: Alessandro Portale <alessandro.portale@digia.com>