Fix for KT-6383: Can't access a private static member of class object

#KT-6383 Fixed

compiler/testData/codegen/boxWithStdlib/platformStatic/syntheticAccessor.kt

@@ -0,0 +1,17 @@
+import kotlin.platform.*
+
+class C {
+    class object {
+        private platformStatic fun foo(): String {
+            return "OK"
+        }
+    }
+
+    fun bar(): String {
+        return foo()
+    }
+}
+
+fun box(): String {
+    return C().bar()
+}