[tz] New leapseconds.awk doesn't work on macOS

[Steffen Nurpmeso]

Steffen Nurpmeso wrote in <20200111204437.3LtvV%steffen at sdaoden.eu>:
 |Guy Harris wrote in <4EDFA3A5-DA50-41BE-A248-EB850CB3A581 at alum.mit.edu>:
 ||On Jan 10, 2020, at 10:26 PM, enh via tz <tz at iana.org> wrote:
 ||> NetBSD already supported regular expressions in RS, and they
 ||> upstreamed that to one-true-awk last year
 ...
 |Debian systems use a historic mawk implementation worth
 |testing against, as it has no gsub and does not have character

Correction.  gsub it has.

--steffen
|
|Der Kragenbaer,                The moon bear,
|der holt sich munter           he cheerfully and one by one
|einen nach dem anderen runter  wa.ks himself off
|(By Robert Gernhardt)