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
        git remote add jic23-iio https://git.kernel.org/pub/scm/linux/kernel/git/jic23/iio.git
        git fetch jic23-iio togreg
        git checkout jic23-iio/togreg
        b4 shazam https://lore.kernel.org/r/20241130174212.3298371-2-paulk@sys-base.io
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um SHELL=/bin/bash drivers/iio/light/