This upstream commit is needed to get pytz building again:

commit 07aa4d962dae5cb7ced4f61fe85a9001a01676df
Author: Stuart Bishop <stuart@stuartbishop.net>
Date: Sat Aug 13 12:00:26 2022 +1000

Revert inclusion of PACKRATDATA=backzone

Per https://github.com/python/tzdata/issues/53#issuecomment-1213628767

I chose to include backzone in pytz in an attempt to head off problems:

Changes to past timestamps

Finish moving to 'backzone' the location-based zones whose
timestamps since 1970 are duplicates; adjust links accordingly.
This change ordinarily affects only pre-1970 timestamps, and with
the new PACKRATLIST option it does not affect any timestamps.
In this round the affected zones are Antarctica/Vostok,
Asia/Brunei, Asia/Kuala_Lumpur, Atlantic/Reykjavik,
Europe/Amsterdam, Europe/Copenhagen, Europe/Luxembourg,
Europe/Monaco, Europe/Oslo, Europe/Stockholm, Indian/Christmas,
Indian/Cocos, Indian/Kerguelen, Indian/Mahe, Indian/Reunion,
Pacific/Chuuk, Pacific/Funafuti, Pacific/Majuro, Pacific/Pohnpei,
Pacific/Wake and Pacific/Wallis, and the affected links are
Arctic/Longyearbyen, Atlantic/Jan_Mayen, Iceland, Pacific/Ponape,
Pacific/Truk, and Pacific/Yap.

This upstream change modifies some of the pre-1970 transitions in obscure
ways that almost zero users will actually care about, and where quite
likely dubious in any case. Such as the times pre-1970 when Belfast was
not on London time or when Amsterdam switched from being 18-20 minutes
ahead of GMT to GMT. Changes to historical timezones has always happened
in the upstream database, and normally they are called corrections
(which only causes breakage if you area storing wallclock times rather
than UTC timestamps).