reproduce (this is a W=1 build):
        mkdir -p ~/bin
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install um cross compiling tool for clang build
        # apt-get install binutils-um-linux-gnu
        git remote add arm64 https://git.kernel.org/pub/scm/linux/kernel/git/arm64/linux.git
        git fetch arm64 for-next/core
        git checkout arm64/for-next/core
        b4 shazam https://lore.kernel.org/r/20230613120047.149573-3-aneesh.kumar@linux.ibm.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=um SHELL=/bin/bash