reproduce (this is a W=1 build):
        git clone https://github.com/intel/lkp-tests.git ~/lkp-tests
        git checkout 03fc07a24735e0be8646563913abf5f5cb71ad19
        b4 shazam https://lore.kernel.org/r/20241025-b4-ovpn-v10-9-b87530777be7@openvpn.net
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc olddefconfig
        ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=powerpc SHELL=/bin/bash drivers/net/ovpn/