Abort build if PR has merge conflicts

[eduard-bagdasaryan]

If PR has merge conflicts, ghprb correctly reports about it:

GitHub pull request #7 of commit 65c03117bb8fc7851a6609f9f3f658c1cfa8f9a5, has merge conflicts

However, instead of entirely aborting build process as I would expect, it starts building PR branch HEAD:

Build started sha1 is original commit.

Evidently, since the job purpose is build only PRs and reflect correct PR build status, it is wrong to build something else and show 'success' status on Github, when actually it can't even be merged into master. Is there any option/workaround here? For the job I configured 'Branch Specifier' as '${sha1}' (as required).

Thanks.