[Issue 21919] darwin: SEGV in core.thread tests on OSX 11

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=21919

--- Comment #4 from Iain Buclaw <ibuclaw at gdcproject.org> ---
This was discovered in December, hence the git commit hashes are 5 months old.

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