This page stores the various jenkins job configuration and helpers to build: http://llvm-jenkins.debian.net/
The infrastructure is described:
https://blog.llvm.org/posts/2021-11-02-apt.llvm.org-moving-from-physical-server-to-the-cloud/
Bugs should be reported on the LLVM bug tracker (label: packaging).
If you have any changes to the llvm.sh script, please run the installation tests before submitting.