reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://github.com/sean-jc/linux/commit/55503e04dc3db68bfba5486acee4a8baa0ef8765
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc sink
        git checkout 55503e04dc3db68bfba5486acee4a8baa0ef8765
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=hexagon olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=hexagon SHELL=/bin/bash drivers/