Ensure LogWriter::writeMessage(std::string&&) is in the overload set of ImmediateFileWriter

Summary: As MSVC correctly warns via C4266, the overload sets of functions in base classes are not part of the overload set in derived classes where you've declared an overload (or override) unless you've explicitly imported it.

Reviewed By: simpkins

Differential Revision: D5260056

fbshipit-source-id: bbbeeea3c13201a3a6eba6e62cfa5a49a9470d43

folly/experimental/logging/ImmediateFileWriter.h

@@ -46,6 +46,7 @@ class ImmediateFileWriter : public LogWriter {
    */
   explicit ImmediateFileWriter(folly::File&& file);
 
+  using LogWriter::writeMessage;
   void writeMessage(folly::StringPiece buffer) override;
 
  private: