[fuchsia] Add missing entrypoint annotation

Change-Id: Ic4a4c0e65d9b1a93528533c2c17dc10653d4ee4e
Reviewed-on: https://dart-review.googlesource.com/c/84441
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Zach Anderson <zra@google.com>
diff --git a/runtime/bin/namespace_patch.dart b/runtime/bin/namespace_patch.dart
index 488aaf5..f28c104 100644
--- a/runtime/bin/namespace_patch.dart
+++ b/runtime/bin/namespace_patch.dart
@@ -32,6 +32,7 @@
 }
 
 @patch
+@pragma("vm:entry-point")
 class _Namespace {
   @patch
   @pragma("vm:entry-point")