CI Pipeline sometimes segfaults on debian:9

Background

We have observed that the CI pipeline can fail some times on debian, like seen in buildstream-docker-images#24 (closed).

@tpollard recalls that one of his pipelines also seg faulted on debian.

Task description

• Figure out the cause of the failures
• Fix them, if possible

Acceptance Criteria

It will be difficult to be certain about this as it is not easily reproducible.

---