reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git/commit/?id=01f609820dfd3182c99ce8a00723ca23798a8056
        git remote add boqun https://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git
        git fetch --no-tags boqun rust-sync
        git checkout 01f609820dfd3182c99ce8a00723ca23798a8056

        # 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