Update mac build machines

[ericstj]

MacOS build agents are no longer supported -- actions/runner-images#13046

This updates to use the latest, while still not "floating" so that we have deterministic behavior.

I added CMAKE_OSX_DEPLOYMENT_TARGET to ensure we still target macOS 13 (implicit before).

I kept the Helix queues at 13 to ensure we still run there.

[Copilot]

Pull Request Overview

This PR updates the macOS build infrastructure from macOS-13 to macOS-15 in response to the deprecation of macOS-13 build agents. The key changes ensure builds run on supported infrastructure while maintaining backward compatibility with macOS 13 as a deployment target.

• Updates all Azure DevOps pipeline configurations to use macOS-15 build agents
• Adds explicit CMAKE_OSX_DEPLOYMENT_TARGET setting to maintain macOS 13 as the minimum deployment target
• Updates CMake comment to clarify bidirectional cross-compilation capability

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
src/Native/CMakeLists.txt	Adds explicit macOS 13 deployment target and updates comment to clarify bidirectional cross-compilation
build/vsts-ci.yml	Updates MacImage variable from macOS-13 to macOS-15
build/.night-build.yml	Updates nightly build vmImage from macOS-13 to macOS-15
.vsts-dotnet-ci.yml	Updates vmImage to macOS-15 for both AMD64 and ARM64 job configurations

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.02%. Comparing base (de4eba2) to head (e79845f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #7558      +/-   ##
==========================================
- Coverage   69.02%   69.02%   -0.01%     
==========================================
  Files        1482     1482              
  Lines      274096   274096              
  Branches    28266    28266              
==========================================
- Hits       189193   189191       -2     
+ Misses      77521    77518       -3     
- Partials     7382     7387       +5     

Flag	Coverage Δ
Debug	69.02% <ø> (-0.01%)	⬇️
production	63.31% <ø> (-0.01%)	⬇️
test	89.47% <ø> (ø)

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see 5 files with indirect coverage changes

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[tarekgh]

LGTM, Thanks!

[ericstj]

/backport to release/5.0

[github-actions]

Started backporting to release/5.0 (link to workflow run)