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
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git/commit/?id=9b54b70265f4d8c913fa8c5c85bbb241524f92f5
        git remote add mel https://git.kernel.org/pub/scm/linux/kernel/git/mel/linux.git
        git fetch --no-tags mel sched-preemptnext-v1r8
        git checkout 9b54b70265f4d8c913fa8c5c85bbb241524f92f5
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash kernel/sched/