Make processConfigs function pure virtual (facebookincubator#10827)

Summary:
to enforce every data format implement its own processConfigs functions

Pull Request resolved: facebookincubator#10827

Reviewed By: xiaoxmeng

Differential Revision: D61743118

Pulled By: kewang1024

fbshipit-source-id: aa1d0b2ea12deaf5b2c2f2ee16827bd6c5a73f38

velox/dwio/common/Options.h

@@ -622,7 +622,7 @@ struct WriterOptions {
   // process format-specific session and connector configs.
   virtual void processConfigs(
       const config::ConfigBase& connectorConfig,
-      const config::ConfigBase& session) {};
+      const config::ConfigBase& session) = 0;
 
   virtual ~WriterOptions() = default;
 };