Supply an explicit default dtor impl

Reviewed By: yfeldblum

Differential Revision: D6142252

fbshipit-source-id: 9ac98585a92299ca5915982c65c7d2cfa68bf60f

folly/Executor.h

@@ -28,7 +28,8 @@ using Func = Function<void()>;
 /// threadsafe.
 class Executor {
  public:
-  virtual ~Executor() = default;
+  // Workaround for a linkage problem with explicitly defaulted dtor t22914621
+  virtual ~Executor() {}
 
   /// Enqueue a function to executed by this executor. This and all
   /// variants must be threadsafe.