The date in the .TH line of jq.1.prebuilt changed whenever the manual was
regenerated in a new month, causing merge conflicts between pull requests
that touch the manual, and it did not reflect the release date anyway.
Generate the committed man page without a date.
Stamp the date into jq.1 at build time instead, taking it from the current
commit, or from SOURCE_DATE_EPOCH where that is set, so that release
tarballs and distribution builds still carry one and the behaviour added
in #3514 is kept. Write it in UTC and in ISO 8601 rather than the previous
"%B %Y", for which mandoc reports "cannot parse date, using it verbatim".
itchyny
17b87d25c7