[box-tests] Added a reproducer for #KT-64139

compiler/testData/codegen/box/coroutines/varSpilling/kt64139.kt

@@ -0,0 +1,33 @@
+// WITH_STDLIB
+// WITH_COROUTINES
+import helpers.*
+import kotlin.coroutines.*
+import kotlin.coroutines.intrinsics.*
+
+suspend fun suspendHere(): Unit = suspendCoroutineUninterceptedOrReturn { x ->
+    x.resume(Unit)
+    COROUTINE_SUSPENDED
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(EmptyContinuation)
+}
+
+class Data(val x: Int)
+
+fun box(): String {
+    var result = ""
+
+    builder {
+        var data = Data(0)
+        var done = false
+        do {
+            data = Data(1)
+            suspendHere()
+            done = true
+        } while (!done)
+        result = if (data.x == 1) "OK" else "fail"
+    }
+
+    return result
+}