infinitebash

I agree, an LTS kernel makes more sense. I've replaced the one kernel submodule with two (one mainline and one LTS) and modified the Makefile to use the LTS kernel...

`graal-jvmci-8` doesn't seem to be maintained anymore ([see here](https://github.com/graalvm/graal-jvmci-8)). It might make more sense to get a binary build from [here](https://github.com/graalvm/graalvm-ce-builds/releases).