Use cmake instead of zlib's configure

[ghost]

A very simple change. This has two advantages:

• cmake will complain giving a proper error message if the toolchain is not installed beforehand
• allows out of source build

Ref: #9

[maxdev1]

Hi @remyabel! Thank you for your contribution :+1: There is an issue I see with this change though. It makes the toolchain dependant of an additional third party software, in this case CMake. Once we come to the point of trying to make Ghost self-hosting, this could lead to issues because we would need to port CMake to Ghost, too. I think a better option would be to create an additional port (maybe call it zlib-cmake) and add it to the repository. This way you can decide to either use the old way to build it or use CMake. What do you think? Greets!

[ghost]

Hello. In that case, I think it's better to just patch the zlib configure to have a better error message.