[minor][egg]: Updating build script to macos15 and xcode 16.4

[fidelianawar]

PR Title Format

Required Format: [Keyword1] [Keyword2]: Description

• Keyword1: major, minor, or patch (case-insensitive)
• Keyword2: feature, bugfix, engg, or tests (case-insensitive)

Examples:

• [MAJOR] [Feature]: new API
• [minor] [bugfix]: fix crash
• [PATCH] [tests]: add coverage

Proposed changes

Fix failing pipeline for [Broker] MSAL submodule check v2 by updating to newer version of Xcode and macOS

Type of change

• Feature work
• Bug fix
• Documentation
• Engineering change
• Test
• Logging/Telemetry

Risk

• High – Errors could cause MAJOR regression of many scenarios. (Example: new large features or high level infrastructure changes)
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• Small – No issues are expected. (Example: Very small bug fixes, string changes, or configuration settings changes)

Additional information

[azure-pipelines]

This pull request does not update CHANGELOG.md.

Please consider if this change would be noticeable to a partner or user and either update CHANGELOG.md or resolve this conversation.

[Copilot]

Pull request overview

Updates the Azure Pipelines broker submodule validation job to run on newer macOS hosted agents and use a newer Xcode, aligning CI configuration with the intended build environment for MSAL/broker integration checks.

Changes:

• Switch Azure Pipelines hosted agent image from macOS-14 to macOS-15.
• Update Xcode selection from Xcode_15.4 to Xcode_16.4 (including the visionOS SDK download step).

Comments suppressed due to low confidence (1)

azure_pipelines/broker_submodule_check.yml:152

• The comment above the visionOS SDK download step still references the macos-14 VM image (and a TODO about macos-14-arm64), but this job now runs on macOS-15. Please update/remove the comment/TODO so it accurately reflects why this step is needed on the current agent image.

# The following is needed to install the visionOS SDK on macos-14 vm image which
# doesn't have visionOS installed by default.
# TODO: Remove when macos-14-arm64 is supported on ADO.
  - task: Bash@3