BC native tests port to Konan's TestRunner

backend.native/tests/runtime/basic/empty_substring.kt

@@ -1,4 +1,8 @@
-fun main(args : Array<String>) {
+package runtime.basic.empty_substring
+
+import kotlin.test.*
+
+@Test fun runTest() {
     val hello = "Hello world"
     println(hello.subSequence(1, 1).toString())
 }