JIT.IL_Conformance throws NullReferenceException

[kunalspathak]

  Discovering: JIT.IL_Conformance.XUnitWrapper (method display = ClassAndMethod, method display options = None)
  Discovered:  JIT.IL_Conformance.XUnitWrapper (found 404 test cases)
  Starting:    JIT.IL_Conformance.XUnitWrapper (parallel test collections = on, max threads = 8)
Unhandled exception. System.NullReferenceException: Object reference not set to an instance of an object.
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.ExecutionContextCallback(Object s) in System.Private.CoreLib.dll:token 0x6004829+0x0
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in System.Private.CoreLib.dll:token 0x6002916+0x40
--- End of stack trace from previous location ---
   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state) in System.Private.CoreLib.dll:token 0x6002916+0x80
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext(Thread threadPoolThread) in System.Private.CoreLib.dll:token 0x600482d+0x3f
   at System.Runtime.CompilerServices.AsyncTaskMethodBuilder`1.AsyncStateMachineBox`1.MoveNext() in System.Private.CoreLib.dll:token 0x600482c+0x0
   at System.Threading.Tasks.AwaitTaskContinuation.<>c.<.cctor>b__17_0(Object state) in System.Private.CoreLib.dll:token 0x6002db8+0x0
   at System.Threading.Tasks.AwaitTaskContinuation.RunCallback(ContextCallback callback, Object state, Task& currentTask) in System.Private.CoreLib.dll:token 0x6002db0+0x13
--- End of stack trace from previous location ---
   at System.Threading.Tasks.Task.<>c.<ThrowAsync>b__140_1(Object state) in System.Private.CoreLib.dll:token 0x6002d46+0x0
   at System.Threading.QueueUserWorkItemCallbackDefaultContext.Execute() in System.Private.CoreLib.dll:token 0x6002a89+0x14
   at System.Threading.ThreadPoolWorkQueue.Dispatch() in System.Private.CoreLib.dll:token 0x6002a63+0xb2
   at System.Threading.PortableThreadPool.WorkerThread.WorkerThreadStart() in System.Private.CoreLib.dll:token 0x6002b3e+0x57
   at System.Threading.Thread.StartCallback() in System.Private.CoreLib.dll:token 0x60026de+0xe
/tmp/helix/working/B7DD0A57/p/scripts/f4743c61301a4515b5621c363a062153/execute.sh: line 15: 90018 Abort trap: 6           (core dumped) dotnet $CORE_ROOT/xunit/xunit.console.dll JIT/IL_Conformance/JIT.IL_Conformance.XUnitWrapper.dll -parallel collections -nocolor -noshadow -xml testResults.xml -trait TestGroup=JIT.IL_Conformance

There are around 40 failures in last 30 days.

https://runfo.azurewebsites.net/search/tests/?q=started%3A%7E30++targetbranch%3Amain+definition%3A655+kind%3Arolling+result%3Afailed+name%3A%22IL_Conformance%22

[dotnet-issue-labeler]

I couldn't figure out the best area label to add to this issue. If you have write-permissions please help me learn by adding exactly one area label.

[kunalspathak]

@dotnet/jit-contrib

[BruceForstall]

I see a couple more of these for OSX/arm64 JitStressRegs=2/0x10:

https://dev.azure.com/dnceng/public/_build/results?buildId=1262314&view=ms.vss-test-web.build-test-results-tab&runId=37412374&resultId=110794&paneView=dotnet-dnceng.dnceng-build-release-tasks.helix-test-information-tab

[BruceForstall]

This is a dup of #51250