reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?id=3b6f99a94b04b389292590840d96342b7dd08941
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch --no-tags tip x86/boot
        git checkout 3b6f99a94b04b389292590840d96342b7dd08941
        # 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