Fix wrong initialization of is_loaded in LibraryPrefix.

runtime/vm/clustered_snapshot.cc

Index: runtime/vm/clustered_snapshot.cc
diff --git a/runtime/vm/clustered_snapshot.cc b/runtime/vm/clustered_snapshot.cc
index 41cfa90212a158266c1e8b630c2eaf905990c5c1..d9e65ad479666f2d11549b0fe08dc149498abdc5 100644
--- a/runtime/vm/clustered_snapshot.cc
+++ b/runtime/vm/clustered_snapshot.cc
@@ -2824,7 +2824,7 @@ class LibraryPrefixDeserializationCluster : public DeserializationCluster {
       }
       prefix->ptr()->num_imports_ = d->Read<uint16_t>();
       prefix->ptr()->is_deferred_load_ = d->Read<bool>();
-      prefix->ptr()->is_loaded_ = false;
+      prefix->ptr()->is_loaded_ = !prefix->ptr()->is_deferred_load_;
     }
   }
 };