cmake instruction on MSYS2 possibly incorrect

[mnadareski]

When attempting to run cmake on MSYS2, I needed to run cmake .. -G "MSYS Makefiles" instead of cmake .. in order for zlib to be properly found. This may be a quirk with my version, but I felt it was worth mentioning.

[JayFoxRox]

It's not an issue in this project.

It's something that bothers me in all my projects: MSYS CMake always needs you to explicitly switch the generator. I'm not sure why CMake is not using MSYS makefiles as default.

I'll keep this issue opened because we should still fix the documentation (to include environment specific instructions) or, preferably, provide binary releases.