[Development] buildsystem branches (about to be) integrated

[Rohan McGovern]

Oswald Buddenhagen said:
> moin,
> 
> the buildsystem branch of qtbase is currently being integrated. this is
> ~120 commits worth of qmake & project file fixes and cleanups. there are
> some changes to how modularization (in particular configure tests) is
> handled, and cross-building should be supported without hacks finally.
> 
> the immediate impact:
> - lots of build scripts which employ various hacks will instantly
>   break. don't panic and (mostly) just delete some code from them.
>   use
>       configure -xplatform <spec> -sysroot <root>
>       make
>   as you would intuitively expect. don't play tricks with funny qmake
>   and make invocations.
> - the other modules will spit out lots of warnings now.
>   *DON'T* do anything about them for now. i have patches prepared for
>   all modules already. i will explicitly add the module owners to the
>   reviews. *don't* stage anything yourself.
>   once my patches are through, there will be still some warnings left.
>   you'll be invited to fix them at this point.
> - some build configurations will work even worse than before until
>   everything is integrated. the only variants which are expected to be
>   safe are developer builds without -prefix and module-by-module builds
>   with -prefix.
> 
> catch me on IRC if something breaks for you and no obvious solution
> seems to help. but remember that not every breakage is due to this
> branch being integrated. ;)

The qtbase merge has caused examples and tests to be silently disabled
in all Linux and Mac CI builds.  That is fixed by
https://codereview.qt-project.org/29088 .  Please refrain from staging
risky changes until that is integrated.

Windows builds and projects other than qtbase seem to be unaffected.