PostgreSQL on s390x on Debian and Ubuntu

Debian has a long history of supporting [diverse machine architectures](https://www.debian.org/ports/), but the number of architectures supported on [apt.postgresql.org](https://apt.postgresql.org), the repository for PostgreSQL on Debian and Ubuntu, has only been growing slowly. So far, this has been amd64 (Intel/AMD x86_64), ppc64el (IBM POWER), and arm64 (Arm aarch64). The old i386 (Intel 32-bit x86) port is still there, but only for the oldest release (and Debian unstable).

Today, I am happy to announce that the family is growing again, with the addition of [IBM's z-series](https://en.wikipedia.org/wiki/IBM_Z) architecture, called "s390x" in Debian terms.

A build machine has been provided by Marist College's [LinuxOne cloud](https://linuxone.cloud.marist.edu/). Preparations to get the architecture set up have been running since earlier this year. Initially, there were some stability problems with the newer PostgreSQL versions, but these have been tackled with patches provided by the PostgreSQL hackers community. Thanks to CYBERTEC PostgreSQL for supporting me working on this!

The s390x architecture is now fully supported for Debian and Ubuntu on apt.postgresql.org.

Cheers,
Christoph