reproduce (this is a W=1 build):
        mkdir -p ~/bin
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        git remote add staging https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/staging.git
        git fetch staging staging-testing
        git checkout staging/staging-testing
        b4 shazam https://lore.kernel.org/r/PH7PR11MB7643F9F5DBB6781022CC4F4DBCE1A@PH7PR11MB7643.namprd11.prod.outlook.com
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang ~/bin/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/staging/octeon/