reproduce (this is a W=1 build):
        # https://github.com/sean-jc/linux/commit/c7de2d2c0cab7d890294b5437faf1bccb6bc978d
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc x86/cleanup_smp_nmi_shootdown
        git checkout c7de2d2c0cab7d890294b5437faf1bccb6bc978d
        # 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 arch/x86/kernel/