[InterNetNews/inn] e172ed: version.h: Use the date of the latest commit

[Julien ÉLIE]

  Branch: refs/heads/main
  Home:   https://github.com/InterNetNews/inn
  Commit: e172ede3268a8aab357fbb69e1756af7ec7d4104
      https://github.com/InterNetNews/inn/commit/e172ede3268a8aab357fbb69e1756af7ec7d4104
  Author: Julien ÉLIE <Julien-Elie at users.noreply.github.com>
  Date:   2022-11-18 (Fri, 18 Nov 2022)

  Changed paths:
    M support/mkversion

  Log Message:
  -----------
  version.h: Use the date of the latest commit

Ensure a reproducible build by using a date which depends on the source code,
and not the time of the build.