reproduce (this is a W=1 build):
        git remote add rmk-arm git://git.armlinux.org.uk/~rmk/linux-arm
        git fetch --no-tags rmk-arm cex7
        git checkout f958ddacf4e1c4aa03ad01b6abef03501217da1c
        # install s390 cross compiling tool for clang build
        # apt-get install binutils-s390x-linux-gnu
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-18 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=s390 SHELL=/bin/bash drivers/net/phy/