ENV/super: enable deterministic archive generation

[Bo98]

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By "archive" I mean the generation of .a files, like static libraries.

ZERO_AR_DATE tells Apple's tools to set the timestamp within these archives to 0.

[BrewTestBot]

Review period will end on 2021-11-29 at 13:12:44 UTC.

[MikeMcQuaid]

Good shout 👏🏻

[BrewTestBot]

Review period skipped due to critical label.