Alpine Linux 3.21.0 Released

• https://www.alpinelinux.org/posts/Alpine-3.21.0-released.html
• LLVM 19

So, to minimize possible incompatibilities, we only move to a newer llvm for Alpine 3.21. I am working on a PR and I think we still have to hard code to a specific value since installing llvm-dev brings in 17 (and I think we still need to set LLVM_CONFIG and CLANG variables). But is llvm19 the best choice when Alpine has chosen llvm16 for their postgresql 14 and 15 packages?

Ouch, this really isn’t as simple as I thought.

imho: Any progress is good, and it would really be great to avoid unnecessary risks because they are not good for the users either – plus, they require extra support from the maintainers.

For this reason, even the LLVM version chosen by the current Alpine seems fine to me.
In other words:

• pg13...pg16: llvm16
• pg17... : llvm18

Based on this - assuming that edge~=3.21:

$ docker run -it --rm alpine:edge sh -c "apk add postgresql15-jit" | grep llvm
(21/22) Installing llvm16-libs (16.0.6-r8)
$ docker run -it --rm alpine:edge sh -c "apk add postgresql16-jit" | grep llvm
(21/22) Installing llvm16-libs (16.0.6-r8)
$ docker run -it --rm alpine:edge sh -c "apk add postgresql17-jit" | grep llvm
(21/22) Installing llvm18-libs (18.1.8-r1)

PR incoming with the most progressive option: trying them all at llvm19 in Alpine 3.21. Once the Alpine 3.21 images are published to Docker Hub, we can restart the tests to see what works and which should be pulled back on llvm version.