reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux.git/commit/?id=40c3e04e2248c0e5d78d23e6767a1c58d5678eac
        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 40c3e04e2248c0e5d78d23e6767a1c58d5678eac

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 prepare