Ignore C5264 ('const' variable is not used) warning in boringssl.

[jonsimantov]

Description

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

Due to some Windows compiler setting changing, the warning C5264 is coming up in boringssl builds on some Windows runners, which breaks due to the treat-warnings-as-errors flag. This PR adds that warning to the "ignore warnings" list.

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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.

C++ Packaging run: https://github.com/firebase/firebase-cpp-sdk/actions/runs/3586408287

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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.

[github-actions]

❌  Integration test FAILED

Requested by @jonsimantov on commit 5d62222
Last updated: Thu Dec 1 08:35 PST 2022
View integration test log & download artifacts

Failures	Configs
auth	[TEST] [FLAKINESS] [Android] [1/3 os: windows] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT
database	[TEST] [FLAKINESS] [Android] [2/3 os: macos windows] [1/2 android_device: android_target] (1 failed tests)   FirebaseDatabaseTest.TestInfoConnected
firestore	[TEST] [ERROR] [Android] [1/3 os: macos] [1/2 android_device: android_target] [TEST] [FAILURE] [tvOS] [macos] [tvos_simulator] (2 failed tests)   CleanupTest.DocumentChangeIsBlankAfterCleanup   NumericTransformsTest.ServerTimestampAndIncrement [TEST] [FLAKINESS] [Android] [1/3 os: windows] [1/2 android_device: android_target] (1 failed tests)   CRASH/TIMEOUT

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