backend: add tests for duplicated string literals

backend.native/tests/build.gradle

@@ -268,3 +268,15 @@ task abstract_super(type: UnitKonanTest) {
 task vtable1(type: UnitKonanTest) {
     source = "datagen/rtti/vtable1.kt"
 }
+
+task strdedup1(type: RunKonanTest) {
+    goldValue = "true\ntrue\n"
+    source = "datagen/literals/strdedup1.kt"
+}
+
+/* TODO: enable after Unit.toString() gets implemented
+task strdedup1(type: RunKonanTest) {
+    goldValue = "true\ntrue\n"
+    source = "datagen/literals/strdedup1.kt"
+}
+*/

backend.native/tests/datagen/literals/strdedup1.kt

@@ -0,0 +1,6 @@
+fun main(args : Array<String>) {
+    val str1 = "Hello"
+    val str2 = "Hello"
+    println(str1 == str2)
+    println(str1 === str2)
+}

backend.native/tests/datagen/literals/strdedup2.kt

@@ -0,0 +1,6 @@
+fun main(args : Array<String>) {
+    val str1 = "kotlin.Unit"
+    val str2 = Unit.toString()
+    println(str1 == str2)
+    println(str1 === str2)
+}