reproduce (this is a W=1 build):
        # https://github.com/sean-jc/linux/commit/faf41e8a0bb349871cbc8e77efe024197509566a
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc x86/xfer_to_guest_mode
        git checkout faf41e8a0bb349871cbc8e77efe024197509566a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/