BC native tests port to Konan's TestRunner

backend.native/tests/codegen/function/plus_eq.kt

@@ -1,9 +1,13 @@
+package codegen.function.plus_eq
+
+import kotlin.test.*
+
 fun plus_eq(a: Int): Int {
   var b = 11
   b += a
   return b
 }
 
-fun main(args: Array<String>) {
+@Test fun runTest() {
   if (plus_eq(3) != 14) throw Error()
 }