Fix clang build

Summary: fix clang build

Test Plan: USE_CLANG make all -j64

Reviewers: horuff, sdong

Subscribers: andrewkr, dhruba

Differential Revision: https://reviews.facebook.net/D57453

tools/ldb_cmd.cc

@@ -1531,24 +1531,24 @@ class InMemoryHandler : public WriteBatch::Handler {
     return Status::OK();
   }
 
-  virtual Status MarkBeginPrepare() {
+  virtual Status MarkBeginPrepare() override {
     row_ << "BEGIN_PREARE ";
     return Status::OK();
   }
 
-  virtual Status MarkEndPrepare(const Slice& xid) {
+  virtual Status MarkEndPrepare(const Slice& xid) override {
     row_ << "END_PREPARE(";
     row_ << LDBCommand::StringToHex(xid.ToString()) << ") ";
     return Status::OK();
   }
 
-  virtual Status MarkRollback(const Slice& xid) {
+  virtual Status MarkRollback(const Slice& xid) override {
     row_ << "ROLLBACK(";
     row_ << LDBCommand::StringToHex(xid.ToString()) << ") ";
     return Status::OK();
   }
 
-  virtual Status MarkCommit(const Slice& xid) {
+  virtual Status MarkCommit(const Slice& xid) override {
     row_ << "COMMIT(";
     row_ << LDBCommand::StringToHex(xid.ToString()) << ") ";
     return Status::OK();