What is CMake
CMake is a cross platform build system, used to generate the native make files / project files for your platform/compiler. Since Arcemu works on many platforms, including Windows, Linux, BSD, OS X, it is ideal for our needs.
You can get CMake for Windows and OS X here: http://www.cmake.org/cmake/resources/software.html
You can get CMake for Linux and BSD using their package managers.
Using CMake to build Arcemu
CMake can be used either natively in a terminal/command prompt, OR using the CMake GUI application.