Draft: .oniro-ci: support direct merge requests in .workspace job

The workspace job has special support for constructing a repo workspace with the changes from the incoming branch applied. This was developed with the GitLab CI option "merge results pipelines" 1 enabled. When that feature is off or unavailable, the git repository constructed by GitLab, as well as the environment variables are somewhat different.

Add logic to detect and work correctly in both cases.

Signed-off-by: Zygmunt Krynicki zygmunt.krynicki@huawei.com