Arti CI jobs fail with "ld terminated with signal 9"

Steps to reproduce

In the arti repo, we have some jobs that build arti (surprising I know). One example is the rust-recent-test-all-features job. This job frequently fails with the error:

  = note: collect2: fatal error: ld terminated with signal 9 [Killed]
          compilation terminated.

An example is at: https://gitlab.torproject.org/tpo/core/arti/-/jobs/1131863

Other jobs can also fail with this error, for example the every-crate CI job. Restarting the job once or twice will typically make the test pass.

It seems possible that we're running out of memory while linking, but I'm not sure of a good way to tell without having ssh access to the machine.

We have a tracking issue in the arti repo at: tpo/core/arti#2152

When did this start?

I think we first noticed this happening around a week ago (the earliest mention I see on IRC was August 27th). This is around the same time that we were running out of disk space, so maybe they're related.