Resize cursor appears on fixed size dialog in Qt 5

Regression from Qt 4.8.

In Qt 4.8, creating a QDialog with a setFixedSize(x,y) will prevent on Windows to have resize cursor arrow in the border of the dialog, it's normal because the user can't do it.

In Qt 5.x, the resize cursors is present even the dialog can't be resize, it's missleading the user.