reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv-linux-gnu
        # clang-21 might not be officially released. Try a lower version if installation fails.
        # https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/commit/?id=f6bff7827a48e59cff1ef98aae72452d65174e0c
        git remote add linux-next https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git
        git fetch --no-tags linux-next master
        git checkout f6bff7827a48e59cff1ef98aae72452d65174e0c
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-21 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash arch/riscv/kvm/ block/ drivers/android/ drivers/char/ drivers/cxl/core/ drivers/gpu/drm/amd/amdgpu/ drivers/hwmon/ drivers/input/ drivers/misc/ drivers/mtd/ubi/ drivers/scsi/ drivers/tty/vt/ drivers/usb/class/ drivers/usb/image/ drivers/vfio/ drivers/video/fbdev/aty/ fs/bcachefs/ fs/crypto/ fs/exfat/ fs/ext4/ fs/fat/ fs/xfs/ io_uring/ kernel/ lib/