reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install arm cross compiling tool for clang build
        # apt-get install binutils-arm-linux-gnueabi
        # https://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git/commit/?id=257f826a691aa9eff8767f0ca5b82a3368b3d02a
        git remote add efi https://git.kernel.org/pub/scm/linux/kernel/git/efi/efi.git
        git fetch --no-tags efi next
        git checkout 257f826a691aa9eff8767f0ca5b82a3368b3d02a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash drivers/firmware/efi/libstub/