tests: fixed Windows support for cumulative_to_delta test case

[mabrarov]

This PR fixes part of issue with building of internal tests on Windows - refer to #11472 (comment). The 2nd part of the fix is located in fluent/cmetrics#258 which after merging needs to be copied (as part of CMetrics library) into this repository.

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Related PRs in other repositories

1. cmetrics: improved Windows support cmetrics#258 for similar changes in CMetrics library.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

Summary by CodeRabbit

• Bug Fixes
  • Improved Windows header handling to avoid conflicts and ensure cleaner builds on Windows.
• Tests
  • Replaced a direct POSIX include in a test with the project's compatibility header to standardize test environment.

[coderabbitai]

📝 Walkthrough

Walkthrough

Adds conditional handling for WIN32_LEAN_AND_MEAN around Windows header inclusions in two cmetrics files and replaces an #include <unistd.h> with #include <fluent-bit/flb_compat.h> in one test file.

Changes

Cohort / File(s)	Summary
Windows Header Compatibility lib/cmetrics/include/cmetrics/cmt_compat.h, lib/cmetrics/src/cmt_atomic_msvc.c	Conditionally define WIN32_LEAN_AND_MEAN if not already defined, include <windows.h>, then undefine it to preserve existing build configurations. No other logic changes.
Test Include Adjustment tests/internal/cumulative_to_delta.c	Replaced #include <unistd.h> with #include <fluent-bit/flb_compat.h>; ensure POSIX symbols (e.g., sleep()) remain available via the compatibility header.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Suggested reviewers

• edsiper
• cosmo0920

Poem

🐰 Hopped through headers, soft and spry,
I tucked a macro, gave it a try.
Included, then cleared—nice and neat,
Swapped an include for fewer feet.
A tiny hop for cleaner builds—so spry!

🚥 Pre-merge checks | ✅ 2 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: fixing Windows support for the cumulative_to_delta test case, which is the primary objective of this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.

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✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[cosmo0920]

Could you remove cmetrics changes from this PR, please?

[mabrarov]

Hi @cosmo0920,

Could you remove cmetrics changes from this PR, please?

This PR is not going to build on Windows without CMetrics changes. Is it acceptable?

Thank you.

[cosmo0920]

Hi @cosmo0920,

Could you remove cmetrics changes from this PR, please?

This PR is not going to build on Windows without CMetrics changes. Is it acceptable?

Thank you.

It depends on @edsiper's decision but we must need to merge the cmetrics' changes at first on paper.
Then, returning back to change Fluent Bit itself.
During waiting for cmetrics's changes, it's OK to break CI results.
After merging cmetrics' patch, we must need to rebase off master and confirm the CI results.

[cosmo0920]

I confirmed that your patch with cmetrics's changes fixes the Windows issue on test case for cumulative_to_delta.

[mabrarov]

da4b352 commit with CMetrics changes (which is copied in fluent/cmetrics#258) was removed from this PR.