reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install um cross compiling tool for clang build
        # apt-get install binutils-um-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://github.com/xinli-intel/linux-fred-public/commit/57b711e7fed167bf1a444aaa218c2987dd315c7d
        git remote add xinli-intel-fred-public https://github.com/xinli-intel/linux-fred-public.git
        git fetch --no-tags xinli-intel-fred-public intel-lkp
        git checkout 57b711e7fed167bf1a444aaa218c2987dd315c7d
        # save the config file
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 ARCH=um