ci: Restrict "success" job to pipelines for MRs (!6492) · Merge requests · Mesa / mesa · GitLab

Michel Dänzer requested to merge daenzer/mesa:ci-success-rules-MRs-only into master Aug 28, 2020

Expected benefits:

No more spurious non-MR pipelines with just this job.
No more warnings from GitLab such as on https://gitlab.freedesktop.org/mesa/mesa/-/pipelines/195778