CI: pin Linux concretization target to x86_64_v3 for buildcache ABI consistency

[Copilot]

CI was reusing buildcache artifacts built for newer microarchitectures (for example x86_64_v4) on x86_64_v3 runners, causing ABI-incompatible dependency reuse during concretization/install. This change standardizes Linux target selection so CI and cache production stay compatible.

• What changed

  • Added a global Linux package constraint in CI Spack config to require target=x86_64_v3 for concretization.
  • Applied at config/ci/packages.yaml under packages: all, so both environment and changed-package CI jobs inherit the same target policy.

• Effect on CI/cache behavior

  • Linux specs produced in CI now converge on a single microarchitecture baseline (x86_64_v3).
  • Buildcache artifacts uploaded by CI align with that baseline, reducing cross-runner ABI mismatches.

packages:
  all:
    require:
    - spec: target=x86_64_v3
      when: platform=linux

[Copilot]

Pull request overview

This PR standardizes Spack concretization on Linux in CI by pinning the microarchitecture target to x86_64_v3, preventing ABI-incompatible reuse of buildcache artifacts produced for newer targets (e.g., x86_64_v4) on x86_64_v3 runners.

Changes:

• Added a packages:all:require rule to enforce target=x86_64_v3 when platform=linux in CI Spack configuration.
• Ensures both environment-based and changed-package CI jobs share the same Linux target baseline via config/ci/packages.yaml.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[wdconinc]

This will fix things like this:

 -           ^davix@0.8.10~ipo~thirdparty build_system=cmake build_type=Release cxxstd=11 generator=make platform=linux os=ubuntu24.04 target=x86_64_v4 %c,cxx=gcc@13.3.0
 -               ^rapidjson@1.2.0-2024-08-16~doc~ipo build_system=cmake build_type=Release commit=7c73dd7de7c4f14379b781418c6e947ad464c818 generator=make patches:=ee123c7 platform=linux os=ubuntu24.04 target=x86_64_v4 %cxx=gcc@13.3.0
 -               ^util-linux-uuid@2.41 build_system=autotools platform=linux os=ubuntu24.04 target=x86_64_v3 %c=gcc@13.3.0

https://github.com/eic/eic-spack/actions/runs/33336035164/job/99322998842?pr=1015#step:12:80