Use system zlib for build tools

[a-maurice]

Description

Provide details of the change, and generalize the change in the PR title above.

After updating to the newer mac runners, the binutil tool has been failing to build correctly because of the zlib version. The zlib version isn't that important to this use case, so use the system one instead.

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Testing

Describe how you've tested these changes. Link any manually triggered Integration tests or CPP binary SDK Packaging Github Action workflows, if applicable.

https://github.com/firebase/firebase-cpp-sdk/actions/runs/26471027607

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Type of Change

Place an x the applicable box:

• Bug fix. Add the issue # below if applicable.
• New feature. A non-breaking change which adds functionality.
• Other, such as a build process or documentation change.

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Notes

• Bug fixes and feature changes require an update to the Release Notes section of release_build_files/readme.md.
• Read the contribution guidelines CONTRIBUTING.md.
• Changes to the public API require an internal API review. If you'd like to help us make Firebase APIs better, please propose your change in a feature request so that we can discuss it together.

[gemini-code-assist]

Note

Gemini is unable to generate a review for this pull request due to the file types involved not being currently supported.

[github-actions]

❌  Integration test FAILED

Requested by @a-maurice on commit 4863376
Last updated: Tue May 26 19:18 PDT 2026
View integration test log & download artifacts

Failures	Configs
auth	[TEST] [FAILURE] [Linux] [x64] [openssl] (2 failed tests)   FirebaseAuthTest.TestUpdateEmailAndPassword   FirebaseAuthTest.TestVerifyBeforeUpdatingEmail

Add flaky tests to go/fpl-cpp-flake-tracker