bug#23776: Perl's .pod files include timestamps, making Perl package builds non-deterministic

[Ludovic Courtès]

Here’s an example:

--8<---------------cut here---------------start------------->8---
$ diff -ru /gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110 
/gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110-check
diff -ru 
/gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110/lib/perl5/5.22.1/x86_64-linux/perllocal.pod
 
/gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110-check/lib/perl5/5.22.1/x86_64-linux/perllocal.pod
--- 
/gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110/lib/perl5/5.22.1/x86_64-linux/perllocal.pod
       1970-01-01 01:00:01.000000000 +0100
+++ 
/gnu/store/fmib129w05hbwbikd7x48s37hvr8nrdf-perl-io-stringy-2.110-check/lib/perl5/5.22.1/x86_64-linux/perllocal.pod
 1970-01-01 01:00:01.000000000 +0100
@@ -1,4 +1,4 @@
-=head2 Thu Jun 16 11:29:36 2016: C<Module> L<IO::Stringy|IO::Stringy>
+=head2 Thu Jun 16 11:29:34 2016: C<Module> L<IO::Stringy|IO::Stringy>
 
 =over 4
 --8<---------------cut here---------------end--------------->8---

The problem is described in <git://git.debian.org/git/reproducible/notes.git>:

--8<---------------cut here---------------start------------->8---
timestamps_in_documentation_generated_by_podman:
  description: |
    The module Pod::Man includes timestamps in its embedded manpages:
    
http://sources.debian.net/src/perl/latest/cpan/podlators/lib/Pod/Man.pm/?hl=1700#L977
    They should be based on the mtime of the original file.
  url: 
https://wiki.debian.org/ReproducibleBuilds/TimestampsInManpagesGeneratedByPodMan
  deterministic: True
--8<---------------cut here---------------end--------------->8---

Ludo’.