reproduce (this is a W=1 build):
        git remote add tip https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git
        git fetch tip sched/core
        git checkout tip/sched/core
        b4 shazam https://lore.kernel.org/r/20260122154227.130767-1-realwujing@gmail.com

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install llvm-dev

        # save the config file
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 ARCH=s390 
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 headers
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-15.1.0 ~/lkp-tests/kbuild/make.cross W=1 -C tools/testing/selftests