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.