Original LKL documentation is here
$ git clone [email protected]:juj/emsdk.git
$ cd emsdk
$ ./emsdk install sdk-tag-1.38.6-64bit
$ ./emsdk activate sdk-tag-1.38.6-64bit
$ source ./emsdk_env.sh
$ cd ..
$ git clone [email protected]:retrage/linux.git --branch=retrage/em-v2 --depth=1
$ cd linux
$ ./build.sh
A Docker image is available.