loading qt_*.qm for RTL languages don't set layout direction to Qt::RightToLeft

When an application loads with a right to left language (e.g. Persian, Arabic) it's layout should be switched to Qt::RightToLeft, too.
There's a translatable string within QApplication class (i.e. tr("QT_LAYOUT_DIRECTION")) responsible for detecting correct layout direction for loaded translation language.

This works on Qt4 but it doesn't work on Qt5.

P.S.: The language file qt_*.qm is loaded successfully because when I add the following line to the application it works correctly:

a.setLayoutDirection(QApplication::tr("QT_LAYOUT_DIRECTION") == QLatin1String("RTL") ? Qt::RightToLeft : Qt::LeftToRight);

A sample file was attached.