reproduce (this is a W=1 build):
        # https://github.com/morimoto/linux/commit/2a60dfb617c1f4f3055ffca329bbb1185e95cd5b
        git remote add morimoto https://github.com/morimoto/linux
        git fetch --no-tags morimoto renesas-lts/v6.18-rc2-2025-10-24-x5h-ironhide
        git checkout 2a60dfb617c1f4f3055ffca329bbb1185e95cd5b

        # install arm64 cross compiling tool for clang build
        # apt-get install binutils-aarch64-linux-gnu
        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=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arm64 SHELL=/bin/bash drivers/mailbox/