nsk/share/MainWrapper.java fixed

Author: Leonid Mesnik

test/hotspot/jtreg/vmTestbase/nsk/share/MainWrapper.java

@@ -46,7 +46,8 @@ public static void main(String[] args) throws Throwable {
         Finalizer finalizer = new Finalizer(new FinalizableObject());
         finalizer.activate();
 
-
+        // Some tests use this property to understand if virtual threads are used
+        System.setProperty("main.wrapper", "Virtual");
 
         Runnable task = () -> {
             try {