[Bug libstdc++/108409] std::chrono::current_zone() doesn't work on AIX

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108409

--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> ---
https://learn.microsoft.com/en-gb/windows/win32/api/timezoneapi/nf-timezoneapi-getdynamictimezoneinformation?redirectedfrom=MSDN
has the same problem. I guess this is why MSVC uses ICU for its
std::chrono::tzdb implementation.