reproduce:
        # https://github.com/jcmvbkbc/linux-xtensa/commit/abd44c5784518efb46e1601d9b04cb5a63506944
        git remote add jcmvbkbc-xtensa https://github.com/jcmvbkbc/linux-xtensa
        git fetch --no-tags jcmvbkbc-xtensa xtensa-6.10-rc2-esp32
        git checkout abd44c5784518efb46e1601d9b04cb5a63506944
        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