CI: enable and collect core dumps in tests

[ansiwen]

This change enables core dumps. If a core dump is created, its backtrace is logged with gdb and it is put into the artifacts together with the test executable.

To see it in action, see #923, which creates a core dump and is based on this PR.

[ansiwen]

Example:
https://github.com/ceph/go-ceph/actions/runs/6816256026/job/18537436259#step:4:886

[ansiwen]

This is ready for review

[phlogistonjohn]

Question: don't core files usually end up outside the container? Is that why you set the core_pattern in the kernel, to make it drop the cores w/in the container?

[ansiwen]

@phlogistonjohn

Question: don't core files usually end up outside the container? Is that why you set the core_pattern in the kernel, to make it drop the cores w/in the container?

I guess that's not true nowadays anymore. I set the pattern to have a deterministic name I can look for. Different distributions have different defaults. But without it, the core dump also ended in the container (tmp or run directory).

Edit: maybe it still would end up outside the container and it only works because this is a bind-mount? Anyway, important is, that is working like this. :-)

[anoopcs9]

Almost looks good to me.

Changes included in the subsequent version.

[phlogistonjohn]

LGTM

[phlogistonjohn]

@ansiwen not sure if you did it on purpose or not, but there's no label yet so it wont automerge. I'll let you add it in case you did it in order to get >1 review.

[phlogistonjohn]

The pr has two approvals, so I added a label myself. ;-)