[tz] Undoing the effect of the new alike-since-1970 patch

[Paul Eggert]

On 6/8/21 10:44 AM, Stephen Colebourne via tz wrote:
> Are you proposing a makefile option to recreate the original source
> files using the data in backzone?

Not byte-for-byte copies, no. Just a functional copy containing the 
equivalent of what the data would have looked like had the new 
alike-since-1970 patch not been installed.

One way to do this would be to generate a file that contains what 
tzdata.zi does, except it omits the effect of the alike-since-1970 
patch. This is basically what Tom Lane was asking for here:

https://mm.icann.org/pipermail/tz/2021-June/030198.html

and I expect it wouldn't be too hard to automate that.