Fix handling of StdCall intrinsic

src/Common/src/TypeSystem/IL/ILProvider.cs

@@ -246,7 +246,7 @@ private MethodIL CreateMethodIL(MethodDesc method)
                 if (((MetadataType)method.OwningType).HasCustomAttribute("System.Runtime.InteropServices", "McgIntrinsicsAttribute"))
                 {
                     var name = method.Name;
-                    if (name == "Call" || name == "StdCall")
+                    if (name == "Call" || name.StartsWith("StdCall"))
                     {
                         return CalliIntrinsic.EmitIL(method);
                     }

src/Common/src/TypeSystem/IL/Stubs/CalliIntrinsic.cs

@@ -18,7 +18,7 @@ public static class CalliIntrinsic
     {
         public static MethodIL EmitIL(MethodDesc target)
         {
-            Debug.Assert(target.Name == "Call" || target.Name == "StdCall");
+            Debug.Assert(target.Name == "Call" || target.Name.StartsWith("StdCall"));
             Debug.Assert(target.Signature.Length > 0
                 && target.Signature[0] == target.Context.GetWellKnownType(WellKnownType.IntPtr));