Those are not supported on Unix configure and are not something
we should support IMO.
Also cleaned up setting a QMAKE_QT_VERSION_OVERRIDE variable
in qconfig.pri that's never used.
Change-Id: I470483660118368abf7bd8aba4a53a25d9ab8a40
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>