Attempt to fix early initialization deadlock in PlatformHelper

src/System.Private.CoreLib/shared/System/Threading/SpinWait.cs

@@ -9,6 +9,7 @@
 // =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
 
 using System.Diagnostics;
+using System.Runtime.CompilerServices;
 using Internal.Runtime.Augments;
 
 namespace System.Threading
@@ -351,6 +352,11 @@ public static bool SpinUntil(Func<bool> condition, int millisecondsTimeout)
     /// <summary>
     /// A helper class to get the number of processors, it updates the numbers of processors every sampling interval.
     /// </summary>
+#if CORERT
+    // The class is used from low-level lock code that participates in the lazy initialization of static constructors,
+    // so any static constructor in this class has to be run early.
+    [EagerStaticClassConstruction]
+#endif
     internal static class PlatformHelper
     {
         private const int PROCESSOR_COUNT_REFRESH_INTERVAL_MS = 30000; // How often to refresh the count, in milliseconds.