The package fails to build on s390x due to failing unit tests:

  failures:
  ---- vhu_scmi::tests::test_event_requests_failure stdout ----
  thread 'vhu_scmi::tests::test_event_requests_failure' panicked at src/vhu_scmi.rs:555:14:
  called `Result::unwrap()` on an `Err` value: InvalidAvailRingIndex
  ---- vhu_scmi::tests::test_event_requests stdout ----
  thread 'vhu_scmi::tests::test_event_requests' panicked at src/vhu_scmi.rs:515:14:
  called `Result::unwrap()` on an `Err` value: InvalidAvailRingIndex
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
  ---- vhu_scmi::tests::test_process_requests stdout ----
  thread 'vhu_scmi::tests::test_process_requests' panicked at src/vhu_scmi.rs:491:14:
  called `Result::unwrap()` on an `Err` value: InvalidAvailRingIndex
  ---- vhu_scmi::tests::test_process_requests_failure stdout ----
  thread 'vhu_scmi::tests::test_process_requests_failure' panicked at src/vhu_scmi.rs:555:14:
  called `Result::unwrap()` on an `Err` value: InvalidAvailRingIndex
  failures:
      vhu_scmi::tests::test_event_requests
      vhu_scmi::tests::test_event_requests_failure
      vhu_scmi::tests::test_process_requests
      vhu_scmi::tests::test_process_requests_failure

This is apparently due to a problem in the underlying libraries.

SCMI support is primarily needed on aarch64. It's also useful in x86_64 host environments, for the purposes of development and testing. It's unlikely that anybody would be bothered by its unavailability on s390x.

Reproducible: Always

Steps to Reproduce:
1. Build vhost-device-scmi on s390x.