reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/thomas.weissschuh/linux.git/commit/?id=677a5fe53cf89d36773e93ebbbb1473fb66592d7
        git remote add thomas-weissschuh https://git.kernel.org/pub/scm/linux/kernel/git/thomas.weissschuh/linux.git
        git fetch --no-tags thomas-weissschuh b4/rv-reactor-signal
        git checkout 677a5fe53cf89d36773e93ebbbb1473fb66592d7
        # install riscv cross compiling tool for clang build
        # apt-get install binutils-riscv-linux-gnu
        # clang-22 might not be officially released. Try a lower version if installation fails.
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-22 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-22 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=riscv SHELL=/bin/bash