Updated DesktopOsHelper.IsMac to work properly on net10 + macOS 26

[reynoldskr]

Changes proposed in this request
Before .NET 10, RuntimeInformation.OSDescription called uname on *nix systems to populate itself. Now it uses a nicer way using the .NET runtime target information, that means that field no longer contains Darwin, so IsMac always returned false. This simply lets that method check for macOs as well.

Testing
I couldn't find any unit tests for this class.

Performance impact
None

[bgavrilMS]

@fengga - smth for you to review

[reynoldskr]

Hey @bgavrilMS / @fengga , any chance of a review here 🙂 ?

[reynoldskr]

This is still broken BTW, and net10 is GA now

[jrr]

This is a real thing blocking me from updating a project to .NET 10.

For what it's worth, here are some values from my machine:

Log.Debug("Platform: {OsVersionPlatform}", Environment.OSVersion.Platform);
Log.Debug("OSDescription: {OsDescription}", RuntimeInformation.OSDescription);
Log.Debug("Is OSX: {IsOsPlatform}", RuntimeInformation.IsOSPlatform(OSPlatform.OSX));

[22:28:40 DBG] Platform: Unix
[22:28:40 DBG] OSDescription: macOS 26.1.0
[22:28:40 DBG] Is OSX: True

(so I think you could either look for the string "macOS" (as in this PR) or call IsOSPlatform)

For comparison, here are the values from .NET 9:

[23:26:02 DBG] Platform: Unix
[23:26:02 DBG] OSDescription: Darwin 25.1.0 Darwin Kernel Version 25.1.0: Mon Oct 20 19:32:41 PDT 2025; root:xnu-12377.41.6~2/RELEASE_ARM64_T6000
[23:26:02 DBG] Is OSX: True