Native: add missing stubs for objc for non-objc targets

Kotlin code for Objective-C interop is always included to stdlib.
It depends on some C++ code. The latter is compiled conditionally -
only for targets supporting Objective-C interop. That might cause
undefined symbols problems when DCE is not enabled.

To deal with it, we usually have trivial stubs in C++ code, used
for targets not supporting Objective-C interop.

This commit adds a couple of such missing stubs.

kotlin-native/runtime/src/main/cpp/ObjCExportCoroutines.mm

@@ -3,16 +3,16 @@
  * that can be found in the LICENSE file.
  */
 
+#import "Memory.h"
+#import "ObjCExport.h"
+#import "ObjCExportErrors.h"
+
 #if KONAN_OBJC_INTEROP
 
 #import <pthread.h>
 #import <Foundation/NSException.h>
 #import <Foundation/NSObject.h>
 
-#import "Memory.h"
-#import "ObjCExport.h"
-#import "ObjCExportErrors.h"
-
 typedef void (^Completion)(id _Nullable, NSError* _Nullable);
 
 extern "C" void Kotlin_ObjCExport_runCompletionSuccess(KRef completionHolder, KRef result) {
@@ -79,4 +79,18 @@ extern "C" void Kotlin_ObjCExport_resumeContinuation(KRef continuation, KRef res
   }
 }
 
+#else
+
+extern "C" void Kotlin_ObjCExport_runCompletionSuccess(KRef completionHolder, KRef result) {
+  RuntimeAssert(false, "Unavailable operation");
+}
+
+extern "C" void Kotlin_ObjCExport_runCompletionFailure(
+  KRef completionHolder,
+  KRef exception,
+  const TypeInfo** exceptionTypes
+) {
+  RuntimeAssert(false, "Unavailable operation");
+}
+
 #endif