reproduce:
        # https://github.com/congwang/linux/commit/af192238f025efad3209ee89f781077db0f66247
        git remote add congwang https://github.com/congwang/linux.git
        git fetch --no-tags congwang xdp_tso
        git checkout af192238f025efad3209ee89f781077db0f66247
        make W=1 O=/tmp/kselftest headers
        make W=1 O=/tmp/kselftest -C tools/testing/selftests
        make W=1 O=/tmp/kselftest -C tools/testing/selftests/bpf