Support configurable library location in qbs build.

And also in the qbs sub-project (for the qbs and qmake builds). This
becomes possible with the qbs submodule update that is part of this
patch.

Change-Id: I8347a8c04a52bcb0682f32d808fb61a90ef3ba72
Reviewed-by: Joerg Bornemann <joerg.bornemann@digia.com>