[Issue 18504] Assert in synchronized crashes with SIGILL on exit

[d-bugmail at puremagic.com]

https://issues.dlang.org/show_bug.cgi?id=18504

--- Comment #1 from FeepingCreature <default_357-line at yahoo.de> ---
Note that this issue appears in a similar form with crashes on GC cleanup of
objects if an assert failed in a synchronized(this) invariant block.

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