[Development] Switch the main "Qt Build System"

[Edward Welbourne]

On 6/9/20 7:22 AM, Bogdan Vatra via Development wrote:
>>> - if you'll not support/trash all .pro/.pri files how we'll push
>>> fixes for 5.15 branch ? Because right now we can't push fixes
>>> directly to 5.15.  branch and all the fixes must go trough dev
>>> branch first.

În ziua de marți, 9 iunie 2020, la 10:35:33 EEST, Joerg Bornemann a scris:
>> All changes that do not apply to Qt6 must go to 5.15.  It's not true
>> that we can't push fixes to 5.15 anymore.

Bogdan Vatra (9 June 2020 12:12)
> If I have a fix which involves also changes to some .pr* files, where
> it should go? In dev I can't push it because you nuked the .pr* files,
> in 5.15 I'm banned.

This is by no means unique to .pr[fio] files: there's lots of code that
we've deleted on dev, that shall need fixes on 5.15.  When a fix gets
picked to 5.15, there is a risk that it'll apply and maybe even
integrate; if so, a follow-up commit only on 5.15 can supply the parts
of the change that aren't present on dev.  More usually, the pick will
get conflicts or fail to integrate, so you'll get the chance to amend
the picked commit on 5.15.  (Even in the first case, if you get the mail
promptly, you can potentially unstage the pick before it gets integrated
and fix it likewise.)

This applies to all the code that's being deleted on dev, including but
by no means limited to qmake's configuration.

	Eddy.