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

[Alexandru Croitor]

> On 19. Nov 2024, at 17:07, Thiago Macieira <thiago.macieira at intel.com> wrote:
> 
> On Tuesday 19 November 2024 02:43:14 Pacific Standard Time Alexandru Croitor 
> via Development wrote:
>> It was brought to my attention that we might be limited by Qt's (or Qt
>> Company's) support for Yocto 4.0 (kirkstone) LTS which ships CMake 3.22.
> 
> As usual... why 4.0? That's from 2.5 years ago. Yes, it's an LTS, but it's old 
> and will be 3 years old when 6.9 is released.

The reasoning I've been told, paraphrasing is the following.

The previous Yocto LTS is still in 3.22 and customers like to stick to older versions (or are forced by HW vendors). 
Upgrading there is not quite that simple as it would affect every OS component as well, not just Qt builds.

meta-qt6 layer, which provides Qt in Yocto, supports different Yocto version for each Qt version. 
So user can more freely choose Qt version for their HW env. 
In Boot2Qt, we try to use most recent version of Yocto, but we still have few HW targets where vendor only supports Yocto/kirkstone, but can still run Qt 6.9 in there.

I also think it would be nice if Qt 6.9 didn't have to be constrained by the old yocto lts version, but i'm waiting for confirmation from above whether it's very important for
QtC.