enable multithreading tests of joins only on 64 bit machines

[bkamins]

@nalimilan - the multithreading tests for 32-bit machine constantly fail. I think it is better to just disable them in that case.

[nalimilan]

Isn't the current try... catch OutOfMemoryError enough?

[bkamins]

First CI run passed cleanly. I closed and reopened it to make sure it is stable.

[bkamins]

Isn't the current try... catch OutOfMemoryError enough?

No because Julia does not handle correctly such try-catch and passes OOM to LLVM which crashes Julia. I discussed it with @vtjnash and @gbaraldi on Slack and it seems it is not fixable.

In short (from Slack):

by catching the exception, you have likely ensured that there is no available memory to reclaim

i.e. because we do try-catch Julia cannot do GC and crashes 😞.

[bkamins]

Thank you!