Use correct class loader to load .kotlin_builtins in reflection

#KT-30749 Fixed

compiler/testData/reflection/classLoaderForBuiltIns/Main.java

@@ -0,0 +1,15 @@
+import java.io.*;
+import java.net.*;
+
+public class Main {
+    public static void main(String[] args) throws Exception {
+        URL[] urls = new URL[args.length];
+        for (int i = 0; i < args.length; i++) {
+            urls[i] = new File(args[i]).toURI().toURL();
+        }
+
+        ClassLoader cl = new URLClassLoader(urls);
+        Class<?> c = cl.loadClass("TestKt");
+        c.getDeclaredMethods()[0].invoke(null);
+    }
+}