DNM: run make check on pull requests

Signed-off-by: Loic Dachary <loic@dachary.org>
This particular node is already pinned by a lot of jobs and having to deal with a `make check` would put it under a lot more load. 

I am not sure if we have defined a `el` or `debian` group, maybe we should so you could at least use the label for the group of machines where you think your script would work and avoid pinning to one.