Null-terminate Collection.toArray destination only in JVM

In other platforms the elements following the collection elements
should not be changed.

As a part of efforts to stabilize Native stdlib.

libraries/stdlib/jvm/src/kotlin/collections/CollectionsJVM.kt

@@ -85,6 +85,14 @@ internal actual inline fun copyToArrayImpl(collection: Collection<*>): Array<Any
 internal actual inline fun <T> copyToArrayImpl(collection: Collection<*>, array: Array<T>): Array<T> =
     kotlin.jvm.internal.collectionToArray(collection, array as Array<Any?>) as Array<T>
 
+internal actual fun <T> terminateCollectionToArray(collectionSize: Int, array: Array<T>): Array<T> {
+    if (collectionSize < array.size) {
+        @Suppress("UNCHECKED_CAST")
+        array[collectionSize] = null as T // null-terminate
+    }
+    return array
+}
+
 // copies typed varargs array to array of objects
 internal actual fun <T> Array<out T>.copyToArrayOfAny(isVarargs: Boolean): Array<out Any?> =
     if (isVarargs && this.javaClass == Array<Any?>::class.java)

libraries/stdlib/jvm/src/kotlin/collections/builders/ListBuilder.kt

@@ -176,12 +176,7 @@ internal class ListBuilder<E> private constructor(
         @Suppress("UNCHECKED_CAST")
         (array as Array<T>).copyInto(destination, 0, startIndex = offset, endIndex = offset + length)
 
-        if (destination.size > length) {
-            @Suppress("UNCHECKED_CAST")
-            destination[length] = null as T // null-terminate
-        }
-
-        return destination
+        return terminateCollectionToArray(length, destination)
     }
 
     override fun toArray(): Array<Any?> {