CMake minimum version update

[David Gobbi]

For cmake 3.22 and later, cmake_minimum_required(VERSION 2.8.12) warns that 2.8.12 is deprecated. The minimum version should be increased to 3.12. This will require updating the systems that are used for nightly testing.

[David Gobbi]

Fixed, as of v0.8.13 the minimum version is cmake 3.12