reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git/commit/?id=1cec1055be7fc2b602f1cde94d772ec822ad6d74
        git remote add tytso-ext4 https://git.kernel.org/pub/scm/linux/kernel/git/tytso/ext4.git
        git fetch --no-tags tytso-ext4 pu
        git checkout 1cec1055be7fc2b602f1cde94d772ec822ad6d74

        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=$HOME/0day COMPILER=gcc-10.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-10.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash