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-riscv64-linux-gnu
        # https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git/commit/?id=8de16c2e3e826f59359da550330149d938e1fb09
        git remote add jirislaby https://git.kernel.org/pub/scm/linux/kernel/git/jirislaby/linux.git
        git fetch --no-tags jirislaby devel
        git checkout 8de16c2e3e826f59359da550330149d938e1fb09
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash drivers/tty/serial/8250/