[Bug]: FileMatcherTest.Unc test fails on macOS

### Issue Description

When I build locally and run tests on macOS 14 on ARM and macOS 13 on Intel, the `Microsoft.Build.UnitTests.FileMatcherTest.Unc` test fails.

### Steps to Reproduce

After confirming local repo is up to date:
1. Run `./build.sh`
1. Run `./build.sh --test`

### Expected Behavior

All tests should pass.

### Actual Behavior

The `Microsoft.Build.UnitTests.FileMatcherTest.Unc` test fails:

```
Failed tests
Microsoft.Build.UnitTests.FileMatcherTest.Unc
Assert.Equal() Failure: Values differ\nExpected: 1\nActual: 0
at Microsoft.Build.UnitTests.FileMatcherTest.MatchDriver(String filespec, String[] excludeFilespecs, String[] matchingFiles, String[] nonmatchingFiles, String[] untouchableFiles, Boolean normalizeAllPaths, Boolean normalizeExpectedMatchingFiles) in /Users/jrdodds/Projects/jrdodds/msbuild/src/Shared/UnitTests/FileMatcher_Tests.cs:line 2426
at Microsoft.Build.UnitTests.FileMatcherTest.MatchDriver(String filespec, String[] matchingFiles, String[] nonmatchingFiles, String[] untouchableFiles) in /Users/jrdodds/Projects/jrdodds/msbuild/src/Shared/UnitTests/FileMatcher_Tests.cs:line 2362
at Microsoft.Build.UnitTests.FileMatcherTest.ValidateFileMatch(String filespec, String fileToMatch, Boolean shouldBeRecursive, Boolean fileSystemSimulation) in /Users/jrdodds/Projects/jrdodds/msbuild/src/Shared/UnitTests/FileMatcher_Tests.cs:line 2533
at Microsoft.Build.UnitTests.FileMatcherTest.ValidateFileMatch(String filespec, String fileToMatch, Boolean shouldBeRecursive) in /Users/jrdodds/Projects/jrdodds/msbuild/src/Shared/UnitTests/FileMatcher_Tests.cs:line 2512
at Microsoft.Build.UnitTests.FileMatcherTest.Unc() in /Users/jrdodds/Projects/jrdodds/msbuild/src/Shared/UnitTests/FileMatcher_Tests.cs:line 1114
at System.RuntimeMethodHandle.InvokeMethod(Object target, Void** arguments, Signature sig, Boolean isConstructor)
at System.Reflection.MethodBaseInvoker.InvokeWithNoArgs(Object obj, BindingFlags invokeAttr)
```

The following files are attached in a .zip file.

- Microsoft.Build.Engine.UnitTests_net9.0_x64.html
- Microsoft.Build.Engine.UnitTests_net9.0_x64.xml

[Build.Engine.UnitTests_net9.0_x64.zip](https://github.com/user-attachments/files/17171653/Build.Engine.UnitTests_net9.0_x64.zip)

### Analysis

I successfully ran the tests on August 5, 2024 so it would seem that something changed after that point.

### Versions & Configurations

macOS Sonoma 14.6.1
Apple M1 Pro (ARM)

macOS Ventura 13.6.9
Intel Core i7