[Chapel Merge] Pin archlinux portability testing to LLVM 21

Branch: refs/heads/main
Revision: ce2a509508ee3f024b413508f6d5dabe6dc37604
Author: arifthpe
Link: Pin archlinux portability testing to LLVM 21 by arifthpe · Pull Request #28552 · chapel-lang/chapel · GitHub
Log Message:
Pin archlinux portability testing to LLVM 21 (#28552)

Pin portability testing on archlinux to install the {llvm,clang}21
packages instead of latest version, which as of 3/7 is now
22
,
which we don't yet support.

Since Archlinux updates so frequently, switch from having both a pinned
and unpinned script to just a pinned script. This should reduce churn
with adding and removing the pinned version as in

and
Additional updates for LLVM 21 by jabraham17 · Pull Request #28002 · chapel-lang/chapel · GitHub.

[trivial, not reviewed]

Compare: Comparing 99309eebb947cb873ed77176c46aef04380cd984...d9ee7efbff3e99ebdbca2994a2dd8498079a9589 · chapel-lang/chapel · GitHub

Diff:
M util/devel/test/portability/apptainer/current/arch/image.def
D util/devel/test/portability/provision-scripts/pacman-llvm.sh
A util/devel/test/portability/provision-scripts/pacman-llvm21.sh
https://github.com/chapel-lang/chapel/pull/28552.diff