[vm] Fix windows build after 722b8391.

Change-Id: Ie6eed25ae159deaf60852d29bca4e35c0084b1ba
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/107403
Reviewed-by: Samir Jindel <sjindel@google.com>
diff --git a/runtime/vm/dart_api_impl_test.cc b/runtime/vm/dart_api_impl_test.cc
index 09e49c0..6fc6940 100644
--- a/runtime/vm/dart_api_impl_test.cc
+++ b/runtime/vm/dart_api_impl_test.cc
@@ -82,7 +82,7 @@
 
   // Wait for 5 seconds to let the kernel service load the snapshot,
   // which should trigger calls to the code observer.
-  sleep(5);
+  OS::Sleep(5);
 
   EXPECT(was_called);
   EXPECT(Dart_Cleanup() == NULL);