tools: assert that the snapshot can be rehashed in node_mksnapshot

PR-URL: https://github.com/nodejs/node/pull/28181
Refs: https://github.com/nodejs/node/pull/27365
Refs: https://github.com/nodejs/node/issues/17058
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Gus Caplan <me@gus.host>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Refael Ackermann (רפאל פלחי) <refack@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

tools/snapshot/snapshot_builder.cc

@@ -96,6 +96,7 @@ std::string SnapshotBuilder::Generate(
     // Must be out of HandleScope
     StartupData blob =
         creator.CreateBlob(SnapshotCreator::FunctionCodeHandling::kClear);
+    CHECK(blob.CanBeRehashed());
     // Must be done while the snapshot creator isolate is entered i.e. the
     // creator is still alive.
     main_instance->Dispose();