Add __isThreadable libRS hack.
diff --git a/lib/bcc/Script.cpp b/lib/bcc/Script.cpp
index a59407b..d9faf02 100644
--- a/lib/bcc/Script.cpp
+++ b/lib/bcc/Script.cpp
@@ -212,6 +212,12 @@
   mCached = cached;
   mStatus = ScriptStatus::Cached;
 
+  // Dirty hack for libRS.
+  // TODO(all):  This dirty hack should be removed in the future.
+  if (cached->isLibRSThreadable() && mpExtSymbolLookupFn) {
+    mpExtSymbolLookupFn(mpExtSymbolLookupFnContext, "__clearThreadable");
+  }
+
   return 0;
 }