reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/morimoto/linux/commit/db060bfe2b3ff750a7d9bd8d44e4eb14e2090b62
        git remote add morimoto https://github.com/morimoto/linux
        git fetch --no-tags morimoto string-helper-2025-07-18
        git checkout db060bfe2b3ff750a7d9bd8d44e4eb14e2090b62
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=csky olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=csky SHELL=/bin/bash drivers/media/rc/