reproduce (this is a W=1 build):
        # https://github.com/Rust-for-Linux/linux/commit/179b3369bc25bb84ee74213e2b4fc5e3c1815375
        git remote add rust https://github.com/Rust-for-Linux/linux
        git fetch --no-tags rust pr/1040
        git checkout 179b3369bc25bb84ee74213e2b4fc5e3c1815375
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=um olddefconfig
        make W=1 O=build_dir ARCH=um SHELL=/bin/bash