[V8] Fix stack alignment corruption for MinGW32 build

BUG: https://bugreports.qt-project.org/browse/QTBUG-31396

Change-Id: Ibf815ab7c1f679b01b347f7141d269a220657968
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>
Reviewed-by: Lars Knoll <lars.knoll@digia.com>