chore: bump minimum cmake version to 3.5 so that cmake 4.0 works out of the box.

[sudonym1]

cmake 4.0 dropped support for versions <3.5. Since 3.5 was released in 2016, seems reasonable to bump the required version from 3.2 to 3.5

[kshepherd]

+1, i currently have to manually update CMakeList min version to get the build to work with my cmake 4 env

[ypogribnyi]

I believe that it's worth changing the version requirement to cmake_minimum_required(VERSION 3.5...4.0) to help with compatibility with future CMake versions. Version 3.5 is the oldest one still accepted by cmake, but everything older than 3.10 is already deprecated and can be removed at any moment.

[clason]

superseded by #158 (thanks!)