[REG 5.7.1 -> 5.8.0] QProcess::startDetached starts cmd.exe without window

1. Build and run this program:

   #include <QApplication>
   #include <QProcess>
   #include <QPushButton>
   
   void startProcess()
   {
       QProcess p;
       p.startDetached("C:\\WINDOWS\\system32\\cmd.exe",
                       QStringList(),
                       "C:\\Users");
   }
   
   int main(int argc, char *argv[])
   {
       QApplication a(argc, argv);
       QPushButton pb("Open Terminal");
       pb.show();
   
       pb.connect(&pb, &QPushButton::clicked,
                  [] () {startProcess();});
   
       return a.exec();
   }
   

2. Click the button.
   Nothing seems to happen. In the task manager you can seeslash. that cmd.exe was started but it does not have a window.

The windows command prompt should be shown. With 5.7.1, this works correctly.

This might have been introduced by https://codereview.qt-project.org/162585/