CompilerServerUnitTests.FallbackToVbc failed in CI

[tmat]

https://dev.azure.com/dnceng/public/_build/results?buildId=580475&view=ms.vss-test-web.build-test-results-tab&runId=18255446&resultId=198963&paneView=debug

System.InvalidOperationException : \r\nThe file 'F:\workspace\_work\1\s\artifacts\tmp\Debug\RoslynTests\a811a6db-db32-4081-90ca-7082f22f7b1b\hello.exe' seems to have been opened in a way that prevents us from deleting it on close.\r\nIs the file loaded as an assembly (e.g. via Assembly.LoadFile)?\r\n\r\nIOException: The process cannot access the file 'F:\workspace\_work\1\s\artifacts\tmp\Debug\RoslynTests\a811a6db-db32-4081-90ca-7082f22f7b1b\hello.exe' because it is being used by another process.\r\n---- System.IO.IOException : The process cannot access the file 'F:\workspace\_work\1\s\artifacts\tmp\Debug\RoslynTests\a811a6db-db32-4081-90ca-7082f22f7b1b\hello.exe' because it is being used by another process.

Stack trace

   at Microsoft.CodeAnalysis.Test.Utilities.DisposableFile.Dispose() in /_/src/Test/Utilities/Portable/TempFiles/DisposableFile.cs:line 42
   at Microsoft.CodeAnalysis.CompilerServer.UnitTests.CompilerServerUnitTests.VerifyResultAndOutput(ValueTuple`2 result, TempDirectory path, String expectedOutput) in /_/src/Compilers/Server/VBCSCompilerTests/CompilerServerTests.cs:line 247
   at Microsoft.CodeAnalysis.CompilerServer.UnitTests.CompilerServerUnitTests.<FallbackToVbc>d__24.MoveNext() in /_/src/Compilers/Server/VBCSCompilerTests/CompilerServerTests.cs:line 375
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
----- Inner Stack Trace -----
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.FileStream.Init(String path, FileMode mode, FileAccess access, Int32 rights, Boolean useRights, FileShare share, Int32 bufferSize, FileOptions options, SECURITY_ATTRIBUTES secAttrs, String msgPath, Boolean bFromProxy, Boolean useLongPath, Boolean checkHost)
   at System.IO.FileStream..ctor(String path, FileMode mode, FileAccess access, FileShare share, Int32 bufferSize, FileOptions options)
   at Microsoft.CodeAnalysis.Test.Utilities.DisposableFile.DeleteFileOnClose(String fullPath) in /_/src/Test/Utilities/Portable/TempFiles/DisposableFile.cs:line 79
   at Microsoft.CodeAnalysis.Test.Utilities.DisposableFile.Dispose() in /_/src/Test/Utilities/Portable/TempFiles/DisposableFile.cs:line 38