reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git/commit/?id=df2d0ce86be9c1b24b0c0f3b5baa68cc3df8ca0e
        git remote add chao https://git.kernel.org/pub/scm/linux/kernel/git/chao/linux.git
        git fetch --no-tags chao bugfix/common
        git checkout df2d0ce86be9c1b24b0c0f3b5baa68cc3df8ca0e
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arc olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=arc SHELL=/bin/bash fs/f2fs/