reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # https://github.com/davidhildenbrand/linux/commit/ff5e85c45e818366d70159de7e6e0d0cc781d2cb
        git remote add davidhildenbrand https://github.com/davidhildenbrand/linux
        git fetch --no-tags davidhildenbrand rmap_id
        git checkout ff5e85c45e818366d70159de7e6e0d0cc781d2cb
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash init/