AbastractProcessStep; Check that creating the build directory worked

Task-number: QTCREATORBUG-13217
Change-Id: I26ac5db79c0e1b6556d085648f9ebc71efae015d
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>
Reviewed-by: Christian Stenger <christian.stenger@digia.com>
ProjectTree: Fix saving of tree expansion state in session

Change-Id: I747b36b0f6a63dcf60eebd95cb1acf72e1629c1c
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>