Create libsampler as V8 sampler library.

src/api.cc

Index: src/api.cc
diff --git a/src/api.cc b/src/api.cc
index a57fa88578b147c154b367bc8cd6631520dad8ed..76bf1099c7fddc3a29061d4e6fcd344bc2bc51a7 100644
--- a/src/api.cc
+++ b/src/api.cc
@@ -7793,6 +7793,12 @@ 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)