* Add test case for #3351 (wrong GMT offset in SunOS/Solaris fallback)
* Fix#3352 (Missing test for Apple / POSIX.1-2024 chooses buggy workaround)
Apple platforms have had the tm_gmtoff-field at least since Mac OS X 10.0,
as are POSIX.1-2024 conforming systems, which are also required to support
it.
This has the unfortunate effect to use the SunOS/Solaris fallback, which
doesn't compute the correct value if the passed value of tm isn't the
current system time, i.e. localtime(::time()) (#3351).
* Fixed GMT offset test
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Co-authored-by: toh <toh@ableton.com>