follow suit to qmake:
- the spec does not need to set the host mode, especially as some
generators are multi-host capable
- the only thing the host mode affects is the path separator, which can
be done directly instead
Change-Id: I618c2c5051234b105c4bc579240aa9f669b4d958
Reviewed-by: Daniel Teske <daniel.teske@nokia.com>
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@nokia.com>