Add a switch to destroy runtime only on shutdown (#4482)

kotlin-native/backend.native/tests/interop/objc/smoke.kt

@@ -10,6 +10,8 @@ import kotlin.native.ref.*
 import kotlin.test.*
 
 fun main(args: Array<String>) {
+    // Test relies on full deinitialization at shutdown.
+    kotlin.native.internal.Debugging.forceCheckedShutdown = true
     autoreleasepool {
         run()
     }