Restructure cmake

[mickem]

There a number of issues with cmake files:

1. build.cmake was a fix for a problem that does not exist any more as there are build profiles in cmake and we should move towards that.
2. Using build.cmake is awkward as properties work "wrong" using that (sometimes defaults overwrite values)
3. cmake minimum version is wrong
4. cmake is messy and unstructured
5. "static" is currently hijacked as "legacy mode" and we should build legacy mode as a dedicated build to allow static and non static to be built freely
6. separate static/dynamic runtime versus linkage (currently they are the same ish)

Feel free to add more issues relating to cmake here

[Fantu]

From the research I had Claude do, the minimum version required seems to be 3.14. There are several features that require higher versions, but they said they're non-blocking. I haven't checked, but it's likely that with some older versions it won't work properly. I've already noticed some things where it doesn't use old, questionable parts, but rather new ones integrated into cmake 4.
Perhaps it should be at least version 3.30, which seems vaguely like the latest version to me, allowing the use of some older, used parts, but it must need to be thoroughly verified.

I think that in the event of a major overhaul, you could consider replacing it with meson, for example.
Most of the packages I maintain or have contributed to in recent years use meson, and it seems simpler and faster (except for a few things that required "tweaks" like those often used in cmake, which have since been improved with new features in more recent version).
However, since it was very simple and fast for most packages, I've never studied meson in depth, so my knowledge and assessment may not be good enough.

However, I think it is important to be able to quickly and easily find all the software required for compilation, the minimum version and any build options. If you can do this while maintaining cmake, keeping that can be fine.

An example of some of the software I maintain in Debian and where is easy and fast find required software for the build and the min. version and also the option:
https://github.com/linuxmint/cinnamon/blob/master/meson.build
https://github.com/linuxmint/cinnamon/blob/master/meson_options.txt
then obviously it also depends a lot on how it is made and maintained, for example it is up to the developers and contributors to update every patch that introduces functions that require higher minimum versions