Logs a warning the first time a problematic class is archived or
unarchived. We expect people to actually fix these issues, so the
performance of the warning isn't too important.
Sample output:
[timestamp] Attempting to archive Swift class '_Test.Outer.ArchivedThenUnarchived', which does not have a stable runtime name.
[timestamp] Use the 'objc' attribute to ensure that the runtime name will not change: "@objc(_TtCC5_Test5Outer22ArchivedThenUnarchived)"
[timestamp] If there are no existing archives containing this class, you can choose a unique, prefixed name instead: "@objc(ABCArchivedThenUnarchived)"
Finishes rdar://problem/32414508
08c2a7a3ac