This update for postgresql12 fixes the following issues:

- Upgrade to 12.10: (bsc#1195680)
  * https://www.postgresql.org/docs/12/release-12-10.html
  * Reindexing might be needed after applying this upgrade, so
    please read the release notes carefully.
- Add constraints file with 12GB of memory for s390x as a workaround. (bsc#1190740)

- Add a llvmjit-devel subpackage to pull in the right versions
  of clang and llvm for building extensions. 
- Fix some mistakes in the interdependencies between the
  implementation packages and their noarch counterpart.
- Update the BuildIgnore section.