[Development] moc output from non-local tool build

[Joerg Bornemann]

On 9/14/21 9:08 PM, Joerg Bornemann wrote:

> I've experimented with this and came up with
> https://codereview.qt-project.org/c/qt/qtbase/+/370958
> which allows to build qtbase dev (6.3.0) against a host Qt 6.1.2.

Doesn't work with non-qtbase repos though.
And this is, because Qt6Foo depends on Qt6FooTools such that in a 
cross-build, find_package(Qt6Core) will trigger find_package(Qt6CoreTools).
The latter will be found in the host Qt. The target Qt does not provide 
Qt6FooTools packages. Changing this is a deep intrusion in the mechanics 
of cross builds, which we don't see the need to do right now.

Instead, we'll address the use case of mixing different versions of host 
Qt and target Qt by adding a switch to turn off any version check.
See discussion at QTBUG-96458.


Cheers,

Joerg