reproduce:
        # https://github.com/sean-jc/linux/commit/666538d29b9c5394d2545cb4052fd3df79e618c8
        git remote add sean-jc https://github.com/sean-jc/linux
        git fetch --no-tags sean-jc x86/ro_memslot_snafu
        git checkout 666538d29b9c5394d2545cb4052fd3df79e618c8
        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