Changed to a standard approach for building

[MihajloPi]

Utilising make for building and installing instead of just using cmake.

[hayguen]

it isn't a good idea to require make or nproc.
these would be available on linux/unix platforms .. but not on windows, when using msvc compiler/toolchain.

i'd prefer keep it as platform independent as possible.
possible go into detail for msvc as here
https://github.com/hayguen/mlpolygen