CI(macOS x64): install libomp from Homebrew Core (drop local libomp.rb)

[asp2286]

Fix macOS x64 CI: install libomp via Homebrew tap (no local formula)

Branch: fix-macos-libomp
Scope: CI only – changes limited to build/ci/job-template.yml (macOS x64 job)

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What & Why

On macOS x64 jobs, our pipeline tries to install OpenMP via a local Homebrew formula:

brew install $(Build.SourcesDirectory)/build/libomp.rb --build-from-source --formula

Recent Homebrew (4.6+) rejects local, untapped formulae and fails with:

Homebrew requires formulae to be in a tap, rejecting:
  /Users/runner/work/1/s/build/libomp.rb
To create a tap, run e.g. brew tap-new <user|org>/<repository>

This does not affect macOS_cross_arm64 jobs because they already use the official homebrew/core formula (brew install libomp).

The fix

For macOS x64 only, switch to the official tap-hosted formula and force a link so the headers and libs are discoverable by our native builds:

# Before (failing; local .rb file)
export HOMEBREW_NO_INSTALLED_DEPENDENTS_CHECK=TRUE && brew install $(Build.SourcesDirectory)/build/libomp.rb --build-from-source --formula

# After (working; official tap)
brew update && brew install libomp && brew link libomp --force

No product/code changes; CI infra-only.

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Validation

• ✅ Verified the failing step is isolated to macOS_x64 with the error above.
• ✅ macOS_cross_arm64 continues to use the official tap and succeeds.
• ✅ Local repro on a GitHub-hosted macOS runner using the new commands installs libomp and exposes headers (/usr/local/opt/libomp/include) and libs (/usr/local/opt/libomp/lib).

Note: Homebrew marks libomp as keg-only. The brew link ... --force step ensures the toolchain sees it without extra flags. If we ever want to avoid --force, we can export:

export CPPFLAGS="-I/usr/local/opt/libomp/include"
export LDFLAGS="-L/usr/local/opt/libomp/lib"

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Risk & Impact

• Risk: Low. The change only affects the CI macOS x64 dependency-install step.
• Impact: Unblocks native builds on macOS x64 by ensuring OpenMP is available.
• No Changes to shipping packages, versioning, public APIs, or runtime behavior.

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Alternative considered

• Creating and maintaining a custom Homebrew tap for libomp.rb. Rejected to avoid long‑term maintenance overhead when the official formula suffices.

---

Change summary

• Update build/ci/job-template.yml macOS x64 path:
  • Replace local formula install with brew update && brew install libomp && brew link libomp --force.
  • No changes to the ARM cross path (already uses official tap).

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How to verify in CI

1. Queue the pipeline for macOS_x64 Debug_Build.
2. Confirm the step Install MacOS build dependencies succeeds, showing:
   • “Pouring libomp…”, “Linking … 6 symlinks created”
3. Validate native build succeeds (CpuMathNative, FastTreeNative, etc.).
4. Ensure no downstream targets rely on OneDalNative on macOS unless explicitly provided (unrelated to this PR).

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Notes for maintainers

• This PR does not modify any source under src/ or packaging. It is safe to service‑merge.
• If future runners transition to Apple Silicon-only, this step remains valid (Homebrew tap still provides libomp).

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Checklist (author)

• CI-only change; no product code.
• macOS x64 path updated; ARM path unchanged.
• Verified the new commands succeed on a runner.
• Added rationale & reproduction details in this PR description.

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Screenshots / logs (for context)

Failure (before):

Error: Homebrew requires formulae to be in a tap, rejecting:
  /Users/runner/work/1/s/build/libomp.rb

Success (after):

==> Fetching downloads for: libomp
==> Pouring libomp--<version>.ventura.bottle.tar.gz
Linking /usr/local/Cellar/libomp/<version>... 6 symlinks created.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.00%. Comparing base (fb39755) to head (4a75fd7).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7501      +/-   ##
==========================================
- Coverage   69.01%   69.00%   -0.01%     
==========================================
  Files        1482     1482              
  Lines      273999   273999              
  Branches    28258    28258              
==========================================
- Hits       189093   189083      -10     
- Misses      77520    77528       +8     
- Partials     7386     7388       +2     

Flag	Coverage Δ
Debug	69.00% <ø> (-0.01%)	⬇️
production	63.29% <ø> (-0.01%)	⬇️
test	89.46% <ø> (ø)

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