Clang diagnostics test failing nightly

[award999]

Failed in last night's nightly https://github.com/swiftlang/vscode-swift/actions/runs/12267257834/job/34227011961

  1) DiagnosticsManager Test Suite
       SourceKit-LSP diagnostics @slow
         Provides clang diagnostics:
     AssertionError [ERR_ASSERTION]: Could not find diagnostic matching:
{"severity":"Error","message":"Use of undeclared identifier 'bar'","range":[{"line":5,"character":10},{"line":5,"character":13}],"source":"clang"}
Diagnostics found:
[]
      at assertHasDiagnostic (test/integration-tests/DiagnosticsManager.test.ts:43:12)
      at Context.<anonymous> (test/integration-tests/DiagnosticsManager.test.ts:1059:13)