[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 #8 from Lionello Lunesu <lio+bugzilla at lunesu.com> ---
$ sw_vers
ProductName:    macOS
ProductVersion: 11.5.2
BuildVersion:   20G95

$ clang --version
Apple clang version 12.0.5 (clang-1205.0.22.11)
Target: x86_64-apple-darwin20.6.0
Thread model: posix
InstalledDir:
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin

$ xcodebuild -version
Xcode 12.5.1
Build version 12E507

$ uname -v
Darwin Kernel Version 20.6.0: Wed Jun 23 00:26:31 PDT 2021;
root:xnu-7195.141.2~5/RELEASE_X86_64

dmd, druntime, Phobos: tag v2.097.2

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