There is a new pull request by mustaqimM against master on the void-packages repository

https://github.com/mustaqimM/void-packages update_postgresql
https://github.com/void-linux/void-packages/pull/18103

postgresql: update to 12.1
[`createlang`](https://stackoverflow.com/questions/52107949/createlang-command-not-found-in-postgres#answer-52109145) and [`droplang`](https://www.postgresql.org/docs/9.6/app-droplang.html) has been deprecated since PostgreSQL 9.1

`plctcl` - Since `createlang` has been deprecated, `CREATE EXTENSION {pltcl,pltclu}` is needed to use it (I don't use this, so could someone please check if it's correct). See [here](https://www.postgresql.org/docs/10/pltcl-overview.html)

New versioning policy since [PostgreSQL 10](https://www.postgresql.org/support/versioning/)

[PostgreSQL 12 release notes](https://www.postgresql.org/docs/current/release-12.html)
[PostgreSQL 11 release notes](https://www.postgresql.org/docs/current/release-11.html)
[PostgreSQL 10 release notes](https://www.postgresql.org/docs/current/release-10.html)

Since more than 1 version has passed, `pg_upgrade` or `pg_dumpall` might be needed to be run on any DBs.

A patch file from https://github.com/void-linux/void-packages/pull/18103.patch is attached