Qt build in jenkins triggers message boxes with help messages from Qt tools

When building Qt in a Jenkins instance, the build stops with a message box that contains the help output of qtpaths.

This resulted from QTBUG-113273 - we now call qtpaths -h when building to check whether the tool can be run.

In Jenkins, the tool somehow doesn't have a console and displays the message box (instead of the help output).

The message box is displayed due to some magic in QCommandLineParser::showHelp() - there's a function that determines whether to use message boxes or not:

// Return whether to use a message box. Use handles if a console can be obtained
// or we are run with redirected handles (for example, by QProcess).
static inline bool displayMessageBox()
{
    if (GetConsoleWindow())
        return false;
    STARTUPINFO startupInfo;
    startupInfo.cb = sizeof(STARTUPINFO);
    GetStartupInfo(&startupInfo);
    return !(startupInfo.dwFlags & STARTF_USESTDHANDLES);
}