[JVM_IR] Determine correct type of empty varargs array.

When calling vararg methods with a generic vararg type without
passing explicit parameters, we have to allocate an empty array
of the right type. We failed to do so previously, as we did
not take the type arguments for the dispatch receiver into
account.

compiler/testData/codegen/boxAgainstJava/varargs/varargsOverride.kt

@@ -0,0 +1,18 @@
+// FILE: A.java
+
+public abstract class A<T> {
+    protected abstract String doIt(T... args);
+
+    public String test(T... args) {
+        return doIt(args);
+    }
+}
+
+// FILE: 1.kt
+
+val a: A<Void> =
+    object : A<Void>() {
+        override fun doIt(vararg parameters: Void): String = "OK"
+    }
+
+fun box(): String = a.test()