reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git/commit/?id=afcb9dd4a55ab82970251b75c2a5461025ed4d8a
        git remote add xiang-erofs https://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
        git fetch --no-tags xiang-erofs dev-test
        git checkout afcb9dd4a55ab82970251b75c2a5461025ed4d8a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 olddefconfig
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash fs/erofs/