Use QVector when creating argv for the command line

MSVC does not support variable length arrays.

Change-Id: I59ef844256eb1b2666331e5ed0411f63e36883ba
Reviewed-by: Jocelyn Turcotte <jocelyn.turcotte@digia.com>
Reviewed-by: Andras Becsi <andras.becsi@digia.com>