reproduce (this is a W=1 build):
        # https://github.com/brauner/linux/commit/3e90c261ca823ef96b9b956d2cd5fe2e9b37629e
        git remote add brauner-github https://github.com/brauner/linux.git
        git fetch --no-tags brauner-github work.kthread.nullfs.split.rebase
        git checkout 3e90c261ca823ef96b9b956d2cd5fe2e9b37629e

        # install sparc64 cross compiling tool for clang build
        # apt-get install binutils-sparc64-linux-gnu
        # clang-23 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=$HOME/0day COMPILER=clang-23 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-23 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 SHELL=/bin/bash fs/