[Development] Qt 6 co-installability with Qt 5

[Sune Vuorela]

On 2020-11-02, Lars Knoll <lars.knoll at qt.io> wrote:
> I honestly don't think renaming all our binaries is an option, certainly not that late in the process. We’ve had Qt 4 and Qt 5 co-installed for a long time as well and while that might not be perfect it was working.
>
> And qtchooser has been working nicely for me (Ubuntu at least uses it).

I pushed quite hard to use it Debian (and ubuntu inherited it), but it
is also a tool that from a packaging perspective gets in the way. Gives
surprises. and weird systems for people.

I also think it is sane to 1) EOL Qt Chooser. 2) Add version numbers to
all public facing executables. (See also e.g. python2 vs python3). and
3) and do it in Qt so that distros are constistent with eachother, with
windows, with mac, and with the Qt documentation.

Oh. And I'm surprised by the Qt-people sudden love of QtChooser - I had
a quite hard battle getting just rudimentary support into Creator to
support the Qt's setup there.

/Sune