reproduce (this is a W=1 build):
        # https://github.com/paulmckrcu/linux/commit/e33488c41be623f7c7ef5b8763e20c45f1364d1c
        git remote add paulmckrcu https://github.com/paulmckrcu/linux
        git fetch --no-tags paulmckrcu dev.2026.09.09a
        git checkout e33488c41be623f7c7ef5b8763e20c45f1364d1c

        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse: v0.6.5-rc1

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.5.0 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.5.0 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=s390 SHELL=/bin/bash kernel/