gitlab: mark s390x-system to allow failures

The system tests (usually qos-test or migration-test) prove to be very
susceptible on the s390x runners. Although we have boosted memory and
virtual CPUs on the runners problems persist. For now mark test as
allow_failure so the its clear on the CI UI when checking test
results.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Message-ID: <20250627112512.1880708-2-alex.bennee@linaro.org>

.gitlab-ci.d/custom-runners/ubuntu-22.04-s390x.yml

@@ -31,7 +31,9 @@ ubuntu-22.04-s390x-all-system:
  timeout: 75m
  rules:
  - if: '$CI_PROJECT_NAMESPACE == "qemu-project" && $CI_COMMIT_BRANCH =~ /^staging/'
+   allow_failure: true
  - if: "$S390X_RUNNER_AVAILABLE"
+   allow_failure: true
  script:
  - mkdir build
  - cd build