Windows: Reintroduce copy of argv.

Since argc/argv is modified by QCoreApplication-derived classes,
a copy of the original arguments is needed for comparison.

This fixes a crash in Qt Quick 2 tests (which use
the -qmljsdebugger=<port> argument) introduced
by dff18b8e

 .

Task-number: QTBUG-30330
Change-Id: Ic145ac923e0a7c504ab16602c8686268e4fd9700
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>