[Development] Proposal to raise the minimum CMake version needed to build and use Qt 6.9

[Tim Blechmann]

>> one point to consider is that cmake does not have any run-time
>> dependencies and it is extremely easy to install independently from the
>> OS: the binaries provided by kitware are fully self-contained and can be
>> installed in parallel to system-provided cmake.
> 
> Installing binaries compiled by someone other than the Linux distribution (and
> thus signed by their repository key) is a non-starter.

the binaries provided by kitware are signed by the same key that's used 
to sign cmake's sources (compare the "Summary files" section on 
https://cmake.org/download/).
that said, iirc cmake is dependency-free and can be built with a one-liner