System.Private.Xml.Tests crashing with SIGSEV

Failing test -- https://helixr18s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-128864-merge-de83ef25c2f0420394/System.Private.Xml.Tests/1/console.8950616e.log?helixlogtype=result

Dump https://helixr18s23ayyeko0k025g8.blob.core.windows.net/dotnet-runtime-refs-pull-128864-merge-de83ef25c2f0420394/System.Private.Xml.Tests/1/core.1000.17?helixlogtype=result

I couldn't analyze that dump - but it could be an environment issue (this is a linux arm64 dump, I have x64 - I tried windows and linux and both failed to load SOS). I also noticed that the build analysis infra that's supposed to auto-analyze and dump to log wasn't working cc @hoyosjs

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1445922
Build error leg or test failing: System.Private.Xml.Tests.WorkItemExecution
Pull request: https://github.com/dotnet/runtime/pull/128864

## Error Message

**DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK** otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using [step by step known issues guidance](https://github.com/dotnet/arcade/blob/main/Documentation/Projects/Build%20Analysis/KnownIssueJsonStepByStep.md).

```json
{
"ErrorMessage": ["xunit.console.dll System.Private.Xml.Tests.dll", "exit code 139"],
"ErrorPattern": "",
"BuildRetry": false,
"ExcludeConsoleLog": false
}
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1445922
**Error message validated:** `[xunit.console.dll System.Private.Xml.Tests.dll exit code 139`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 6/3/2026 4:06:49 PM UTC

### Report
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|0|0|