Abseil's Serenity support is a little limited:
- No support for any timezone shenanigans since protobuf hopefully
doesn't use those. For now, abseil will always believe to be in UTC on
Serenity.
- In most places where explicit platforms need to be added to a list of
supported platforms, Serenity will be missing. Again I only added the
ones that are required for protobuf.
