[Development] Requesting a wip/qt6 branch for QtSerialBus

[Shawn Rutledge]

> On 2 Oct 2018, at 13:08, Oswald Buddenhagen <Oswald.Buddenhagen at qt.io> wrote:
> 
> in fact, the introduction of a respective configure feature (so you
> would #if QT_CONFIG(qt6)) has been on the table for quite a while
> already, but nobody pushed for it yet, presumably because we haven't
> officially started qt6 yet.

Well I think it’s a good idea to do it ASAP.

> note that the qt(core) code is already full of QT_VERSION_CHECK(6,0,0)
> which does effectively the same, but to activate it you would need to
> change .qmake.conf instead of just calling configure -qt6.

I’ve written those once or twice but never actually tried to build that way.  It would be good to really try a few things soon.  (Some things will be a lot of work, so better not wait until there is a time crunch to get Qt 6 done within a few months.)  A configure option sounds like the nicer way to do it, so that I can make a Qt6 shadow build of dev branch at any time.