Fix StackTrace unit test for Release builds

Add the missing "NoInline" attribute to prevent inlining and always retrieve the correct StackTrace.

Author: Sridhar-MS

src/System.Runtime.Extensions/tests/System/Environment.StackTrace.cs

@@ -60,6 +60,7 @@ public static void StaticFrame(object obj)
 
         class TestClass
         {
+            [MethodImpl(MethodImplOptions.NoInlining)]
             public TestClass()
             {
                 EnvironmentStackTrace.StaticFrame(null);