reproduce (this is a W=1 build):
        # https://github.com/nbdd0121/linux/commit/8d994e776994c16396a9bd5ac05891909371457c
        git remote add nbdd0121 https://github.com/nbdd0121/linux
        git fetch --no-tags nbdd0121 vtable-wip
        git checkout 8d994e776994c16396a9bd5ac05891909371457c
        # 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 CLIPPY=1 rustdoc