[Known Build Error] SemanticSearch.ReferenceAssemblies: Error updating baseline because it is being used by another process

## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1390698&view=logs&j=96a50e04-2c20-5562-4d03-6c998a9295de
Build error leg or test failing: Correctness / Correctness_Determinism / Build - Validate determinism
Pull request: https://github.com/dotnet/roslyn/pull/83271

## Error Message

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": "",
"ErrorPattern": "SemanticSearch.ReferenceAssemblies.*Error updating baseline.*because it is being used by another process",
"BuildRetry": true,
"ExcludeConsoleLog": false
}
```

### Known issue validation
**Build: :mag_right:** https://dev.azure.com/dnceng-public/public/_build/results?buildId=1390698
**Error message validated:** `[SemanticSearch.ReferenceAssemblies.*Error updating baseline.*because it is being used by another process`]
**Result validation:** :white_check_mark: Known issue matched with the provided build.
**Validation performed at:** 4/22/2026 11:25:43 AM UTC

### Report
|Build|Repository|Step Name|Console log|Pull Request|
|---|---|---|---|---|
|[1588886](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1588886)|dotnet/roslyn|Build|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1588886/logs/82)|dotnet/roslyn#85222|
|[1557397](https://dev.azure.com/dnceng-public/public/_build/results?buildId=1557397)|dotnet/roslyn|Build|[Log](https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_apis/build/builds/1557397/logs/94)|dotnet/roslyn#83216|
#### Summary
|24-Hour Hit Count|7-Day Hit Count|1-Month Count|
|---|---|---|
|0|1|2|

Start with the linked pull request #83271 and the validated build log for the Correctness_Determinism / Build - Validate determinism leg. Read the known-issues guidance linked in the issue and compare the existing ErrorPattern and retry settings; done means the recurring baseline-locking failure is correctly classified and validated.

Written by the indexing model from the issue text.