reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?id=c3cc47915438797b3342f426772472b7c3dee6df
        git remote add gustavoars https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git
        git fetch --no-tags gustavoars testing/wfamnae-next20251212
        git checkout c3cc47915438797b3342f426772472b7c3dee6df

        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        # clang-22 might not be officially released. Try a lower version if installation fails.
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # apt-get install sparse
        # sparse version: v0.6.4-73-gfbdde312

        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-22 ~/lkp-tests/kbuild/make.cross W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__ -fmax-errors=unlimited -fmax-warnings=unlimited' O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-22 ~/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/bpf/