Create libsampler as V8 sampler library.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index a4e047c9b64a6b9c66c8618a3376f9a5ba12e540..1f759c2f46da47bd1a07a4664bea11d31f7141b2 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -7781,6 +7781,12 @@ void Isolate::VisitExternalResources(ExternalResourceVisitor* visitor) {
 }
 
 
+bool Isolate::IsInUse() {
+  i::Isolate* isolate = reinterpret_cast<i::Isolate*>(this);
+  return isolate->IsInUse();
+}
+
+
 class VisitorAdapter : public i::ObjectVisitor {
  public:
   explicit VisitorAdapter(PersistentHandleVisitor* visitor)