reproduce (this is a W=1 build):
        git remote add samba-ksmbd git://git.samba.org/ksmbd.git
        git fetch --no-tags samba-ksmbd ksmbd-for-next-next
        git checkout 71e7b7a9f9433c5c340eeb8cfaa12a72e2369f73

        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash fs/smb/server/