[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 #3 from Iain Buclaw <ibuclaw at gdcproject.org> ---
Process 65900 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS
(code=2, address=0x100c8cc70)
    frame #0: 0x00007fff203794e0 libsystem_pthread.dylib`___chkstk_darwin + 96
libsystem_pthread.dylib`___chkstk_darwin:
->  0x7fff203794e0 <+96>:  testq  %rcx, (%rcx)
    0x7fff203794e3 <+99>:  popq   %rcx
    0x7fff203794e4 <+100>: retq
libsystem_pthread.dylib`pthread_getspecific:
    0x7fff203794e5 <+0>:   movq   %gs:(,%rdi,8), %rax
Target 0: (test_runner) stopped.
(lldb) bt
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS
(code=2, address=0x100c8cc70)
  * frame #0: 0x00007fff203794e0 libsystem_pthread.dylib`___chkstk_darwin + 96
    frame #1: 0x00007fff20379480 libsystem_pthread.dylib`thread_start + 20
    frame #2: 0x00007fff2a542a9c
libunwind.dylib`libunwind::UnwindCursor<libunwind::LocalAddressSpace,
libunwind::Registers_x86_64>::step() + 476
    frame #3: 0x00007fff2a5446ee libunwind.dylib`_Unwind_RaiseException + 189
    frame #4: 0x00000001001bbeb8 test_runner`_d_throwdwarf at dwarfeh.d:317
    frame #5: 0x0000000100188b84
test_runner`_D4core6thread5fiber19__unittest_L1679_C1FZ9__lambda1MFNaNbNfZv at
fiber.d:1686
    frame #6: 0x000000010018fb85
test_runner`_D4core6thread7context8Callable6opCallMFZv at context.d:46
    frame #7: 0x0000000100187ac5 test_runner`_D4core6thread5fiber5Fiber3runMFZv
at fiber.d:869
    frame #8: 0x000000010018749f test_runner`fiber_entryPoint at fiber.d:157

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