mkdir build
cd build
cmake <path-to-cloned-repo>
cmake --build .
./src/lsystem # or .\src\Debug\lsystem.exe if you're on Windows
CMake >= 3.12
Also, if you're on Linux, you'll need to install dependencies for building SFML specified here.
Ubuntu:
sudo apt install libxrandr-dev libxcursor-dev libudev-dev libopenal-dev libflac-dev libvorbis-dev libgl1-mesa-dev libegl1-mesa-dev
sfml-imgui-template by Elias Daler from here