Run Boehm assertions on CI

[jacob-hughes]

No description provided.

[jacob-hughes]

I've fixed the various test failures here: 77872b6. If all looks good, can I squash?

[ltratt]

Please squash.

[jacob-hughes]

Squashed

[jacob-hughes]

This test failure is to do with the flaky nature of how we test that finalisers have run. We have to remove references to objects in order for them to die and then be finalised and on bencher16, it's enough to create a new on-stack-pointer to overwrite the old one. Unfortunately this doesn't seem to work on CI (because really we're in UB territory here).

The problem is that the last reference to an object in a tight loop sometimes lingers, so I suggest we modify this test from:

assert_eq!(finalisers_run, expected_finalisers_run)

to:

assert!(finalisers_run >= expected_finalisers_run - 1)

[ltratt]

@jacob-hughes Works for me!

[ltratt]

[Provided we add a nice long comment explaining why the test is a bit weaker than one might first expect.]

[jacob-hughes]

How about something like this? 915649d

[jacob-hughes]

Fixed a typo here 4067bc5

[ltratt]

Please squash.

[jacob-hughes]

Squashed