reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        # install um cross compiling tool for clang build
        # apt-get install binutils-um-linux-gnu
        # https://github.com/zen-kernel/zen-kernel/commit/e93bbd136fd055f85e95a1477531a8c9ef4e8bc9
        git remote add zen https://github.com/zen-kernel/zen-kernel
        git fetch --no-tags zen 6.9/zen-sauce
        git checkout e93bbd136fd055f85e95a1477531a8c9ef4e8bc9
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=clang-19 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=um SHELL=/bin/bash drivers/pci/controller/