Update box tests to 1.2.0-rc-39

backend.native/tests/external/codegen/box/when/whenSafeCallSubjectEvaluatedOnce.kt

@@ -0,0 +1,19 @@
+var subjectEvaluated = 0
+
+fun String.foo() = length.also { ++subjectEvaluated }
+
+fun test(s: String?) =
+    when (s?.foo()) {
+        0 -> "zero"
+        1 -> "one"
+        2 -> "two"
+        else -> "other"
+    }
+
+fun box(): String {
+    val t = test("12")
+    if (t != "two") return "Fail: $t"
+    if (subjectEvaluated != 1) return "Fail: subjectEvaluated=$subjectEvaluated"
+
+    return "OK"
+}