reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git/commit/?id=741e95c4b46803e113402223592189848b0ac9c8
        git remote add arnd-playground https://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git
        git fetch --no-tags arnd-playground abi-test
        git checkout 741e95c4b46803e113402223592189848b0ac9c8

        # install um cross compiling tool for clang build
        # apt-get install binutils-um-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-17 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-17 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um SHELL=/bin/bash