ci: expose OpenBLAS build failure logs

[jac0626]

Change Type

• Bug fix
• New feature
• Improvement/Refactor
• Documentation
• CI/Build/Infra

Linked Issue

• Related to [bug](ci): bundled OpenBLAS build intermittently fails across workflows #2507
• Related to [bug](build): retain OpenBLAS diagnostics after TSAN build failures #2559
• Related to [bug](ci): TSAN build fails in bundled OpenBLAS build #2514

What Changed

• Merge stdout and stderr for logged OpenBLAS ExternalProject steps.
• Replay the captured OpenBLAS build log when the ExternalProject step fails.

This keeps successful builds quiet while making intermittent bundled OpenBLAS failures visible in the job log, including failures inside temporary Python build containers.

Test Evidence

• make fmt
• make lint
• make test
• make cov, run tests, and collect coverage
• Other (controlled ExternalProject failure A/B test and git diff --check)

Test details:

Used the repository openblas.cmake with the real OpenBLAS 0.3.24 archive and a controlled nested make command that writes distinct stdout/stderr sentinels, then exits 23.

Before:
  build status: failure
  stdout sentinel in console: 0
  stderr sentinel in console: 0
  sentinels retained in separate openblas-build-{out,err}.log files: yes

After:
  build status: failure
  stdout sentinel in console: 1
  stderr sentinel in console: 1
  both sentinels retained in openblas-build.log: yes
  CMake prints -- Log output is: before replaying the failure: yes

git diff --check: pass

Compatibility Impact

• API/ABI compatibility: none
• Behavior changes: failed logged ExternalProject steps now replay their captured output; successful builds are unchanged

Performance and Concurrency Impact

• Performance impact: none expected
• Concurrency/thread-safety impact: none

Documentation Impact

• No docs update needed
• Updated docs:
  • README.md
  • DEVELOPMENT.md
  • CONTRIBUTING.md
  • Other

Risk and Rollback

• Risk level: low
• Rollback plan: revert the commit to restore separate hidden stdout/stderr logs

Checklist

• I have linked the relevant issues
• No unit test is needed; the CMake behavior was verified with a controlled failure regression probe
• I have considered API compatibility impact
• No documentation update is required
• My commit message follows project conventions

[vsag-bot]

/label status/waiting-for-review
/waiting-on reviewer
/request-review @jiaweizone
/request-review @wxyucs
/request-review @inabao

[mergify]

Merge Protections

🟢 All 2 merge protections satisfied — ready to merge.

Show 2 satisfied protections

🟢 Require kind label

• label~=^kind/

🟢 Require version label

• label~=^version/

[Copilot]

Pull request overview

This PR improves CI diagnostics for the bundled OpenBLAS ExternalProject build by ensuring build logs are both captured in a single stream and automatically replayed into the job output when the ExternalProject step fails, while keeping successful builds quiet.

Changes:

• Enable merged stdout/stderr logging for OpenBLAS ExternalProject steps.
• Enable automatic log replay to the CMake/CI console on ExternalProject failure.

---

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

[LHT129]

LGTM