reproduce (this is a W=1 build):
        # https://github.com/amir73il/linux/commit/b66d24d8d654b23fbadf70e520e34d945219e8e5
        git remote add amir73il https://github.com/amir73il/linux
        git fetch --no-tags amir73il fan_mark_userns
        git checkout b66d24d8d654b23fbadf70e520e34d945219e8e5

        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=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=i386 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-20 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=i386 SHELL=/bin/bash fs/erofs/