VERSION=12 FORCE_DEB_BUILD=1 build fails

[birkb]

because of missing packages in the apt repository Packages file.

• The VERSION=12 FORCE_DEB_BUILD=1 build fails, but version 12.2-2.pgdg100+1 is available in the repo.
• http://apt.postgresql.org/pub/repos/apt/dists/buster-pgdg/12/binary-amd64/Packages does not contain the 12.2-2.pgdg100+1 package.
• apt-cache search postgresql-12 inside the build container shows no packages. apt-cache search postgresql-11 lists 64 packages.

[birkb]

PR713 is affected by the problem. The related Travis job has been failed.

[tianon]

I was looking into this earlier this morning -- this is to make sure that architectures that repository doesn't have binary packages get built for instead, but the problem is that 12.2-2.pgdg100+1 is the latest available version for most architectures except arm64, which has 12.2-3.pgdg100+1. Due to a quirk in how that repository is maintained, only the latter gets listed in the Sources manifest file (so even though http://apt.postgresql.org/pub/repos/apt/pool/main/p/postgresql-12/postgresql-12_12.2-2.pgdg100%2B1.dsc exists, our build doesn't find it because Sources points us at http://apt.postgresql.org/pub/repos/apt/pool/main/p/postgresql-12/postgresql-12_12.2-3.pgdg100%2B1.dsc 😞).

[birkb]

What does it mean for my PR? Is it good enough even if one target fails (for 3rd party reasons)?