Bug#914962: perl: t/porting/manifest.t fails in a git checkout

[Niko Tyni]

Source: perl
Version: 5.28.0-4

When building in a checkout of our Debian git repo
(currently https://salsa.debian.org/perl-team/interpreter/perl ),
t/porting/manifest.t fails because the files in debian/ and
regen-configure/ are not in MANIFEST.

This broke in 5.26.1-1 when debian/skip-upstream-git-tests.diff was
replaced with the upstreamed fixes/packaging_test_skips.diff patch
(included upstream in 5.28), relying on the PERL_BUILD_PACKAGING
environment variable to skip tests specific to the upstream git
repository.

The problem is that find_git_or_skip() in t/test.pl looks at
PERL_BUILD_PACKAGING too late, so it doesn't change the logic of skipping,
only the explanation of why tests get skipped if they do.

Presumably this hasn't been spotted earlier because we almost never
build in git checkouts. I know I mostly just pass a .dsc to sbuild when
building. Still, I think this is worth fixing, preferably upstream as
I don't think the current test.pl change is useful to anybody.
-- 
Niko Tyni   ntyni at debian.org