Parameterize the Java logging formatter class.

Allow subclasses of StartupOptions to override the formatter passed to
the Java logging configuration.  This is to allow us to override this
value internally for Blaze in an attempt to homogenize things.

--
PiperOrigin-RevId: 146668430
MOS_MIGRATED_REVID=146668430
diff --git a/src/main/cpp/startup_options.h b/src/main/cpp/startup_options.h
index b36a70a..7bde6e7 100644
--- a/src/main/cpp/startup_options.h
+++ b/src/main/cpp/startup_options.h
@@ -212,6 +212,9 @@
   // abruptly without proper communication over gRPC.
   bool use_custom_exit_code_on_abrupt_exit;
 
+  // Value of the java.util.logging.FileHandler.formatter Java property.
+  std::string java_logging_formatter;
+
  protected:
   // Constructor for subclasses only so that site-specific extensions of this
   // class can override the product name.  The product_name must be the