[serializer] small fixes for blink snapshot.

include/v8.h

Index: include/v8.h
diff --git a/include/v8.h b/include/v8.h
index 5302f836faaeaf8bf0f9d5d3874bb3e3d5ec74ec..5348ba7e48b32b6beb35ef31db9dd53401c38814 100644
--- a/include/v8.h
+++ b/include/v8.h
@@ -7575,7 +7575,7 @@ class V8_EXPORT V8 {
 /**
  * Helper class to create a snapshot data blob.
  */
-class SnapshotCreator {
+class V8_EXPORT SnapshotCreator {
  public:
   enum class FunctionCodeHandling { kClear, kKeep };