scratch: make wrappable finalizable (match ClosureTracer)

Author: romgrk

cppgc-repro/binding.cc

@@ -1,6 +1,8 @@
 // Minimal reproduction: cppgc::MakeGarbageCollected crashes inside an addon on
 // arm64 macOS. Build with node-gyp; call `make()` from JS.
 #include <cstdio>
+#include <mutex>
+#include <vector>
 #include <node.h>
 #include <v8.h>
 
@@ -9,9 +11,15 @@
 #include "cppgc/visitor.h"
 #include "v8-cppgc.h"
 
+// Match node-gtk's ClosureTracer: non-trivial (mutex + vector + destructor), so
+// cppgc registers a finalizer for it. The trivial version did NOT crash.
 class Wrappable final : public cppgc::GarbageCollected<Wrappable> {
  public:
   void Trace(cppgc::Visitor*) const {}
+  ~Wrappable() { v.clear(); }
+ private:
+  mutable std::mutex m;
+  std::vector<void*> v;
 };
 
 static void Make(const v8::FunctionCallbackInfo<v8::Value>& info) {