windeployqt: Accept a list of positional arguments.

The first argument can be either a binary or a directory containing
the binary. Further arguments can be either libraries or directories
containing libraries (plugins).

Task-number: QTBUG-41670
Change-Id: I48dd157f6404118400948ef019016c2aa6661762
Reviewed-by: Oliver Wolff <oliver.wolff@digia.com>
Reviewed-by: Joerg Bornemann <joerg.bornemann@theqtcompany.com>