reproduce (this is a W=1 build):
        # https://git.kernel.org/pub/scm/linux/kernel/git/martin.lau/bpf-next.git/commit/?id=b735af227349c9ef167cae8acf8bc8864e13f636
        git remote add martin-lau-bpf-next https://git.kernel.org/pub/scm/linux/kernel/git/martin.lau/bpf-next.git
        git fetch --no-tags martin-lau-bpf-next ls.rqspin.v2.2
        git checkout b735af227349c9ef167cae8acf8bc8864e13f636

        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=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 olddefconfig
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-8.5.0 ~/lkp-tests/kbuild/make.cross W=1 O=build_dir ARCH=sparc64 SHELL=/bin/bash kernel/bpf/