After clone do:

git submodule init
git submodule update

... to init all the submodules.

The build system is based on CMake.

cmake -P KRAL/build.cmake

This will show you all the available compile targets. To compile first you need to generate the project and then compile it:

cmake -DN=1 -DG=1 -P KRAL/build.cmake
cmake -DN=1 -DC=1 -P KRAL/build.cmake

The first command generated the first target (N=1) and the second line starts the compilation process.