Fix clang build
Fix clang build

Summary: Fix clang

Test Plan:
USE_CLANG=1 make all -j64

Reviewers: sdong, yhchiang, anthony, rven

Reviewed By: rven

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D50793

wenduo/rocksdb,norton/rocksdb,tsheasha/rocksdb,bbiao/rocksdb,jalexanderqed/rocksdb,tsheasha/rocksdb,Vaisman/rocksdb,Andymic/rocksdb,OverlordQ/rocksdb,norton/rocksdb,wat-ze-hex/rocksdb,OverlordQ/rocksdb,ryneli/rocksdb,facebook/rocksdb,vmx/rocksdb,wenduo/rocksdb,hobinyoon/rocksdb,Vaisman/rocksdb,ryneli/rocksdb,bbiao/rocksdb,norton/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,facebook/rocksdb,Andymic/rocksdb,ryneli/rocksdb,bbiao/rocksdb,facebook/rocksdb,vmx/rocksdb,ryneli/rocksdb,hobinyoon/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,hobinyoon/rocksdb,hobinyoon/rocksdb,flabby/rocksdb,wat-ze-hex/rocksdb,bbiao/rocksdb,tsheasha/rocksdb,ryneli/rocksdb,jalexanderqed/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,wat-ze-hex/rocksdb,tsheasha/rocksdb,hobinyoon/rocksdb,OverlordQ/rocksdb,jalexanderqed/rocksdb,OverlordQ/rocksdb,Vaisman/rocksdb,wenduo/rocksdb,Andymic/rocksdb,wat-ze-hex/rocksdb,jalexanderqed/rocksdb,hobinyoon/rocksdb,facebook/rocksdb,facebook/rocksdb,tsheasha/rocksdb,wat-ze-hex/rocksdb,Vaisman/rocksdb,wat-ze-hex/rocksdb,ryneli/rocksdb,vmx/rocksdb,flabby/rocksdb,Andymic/rocksdb,vmx/rocksdb,SunguckLee/RocksDB,tsheasha/rocksdb,jalexanderqed/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,SunguckLee/RocksDB,flabby/rocksdb,Vaisman/rocksdb,norton/rocksdb,norton/rocksdb,Andymic/rocksdb,Andymic/rocksdb,facebook/rocksdb,ryneli/rocksdb,facebook/rocksdb,norton/rocksdb,facebook/rocksdb,wat-ze-hex/rocksdb,wat-ze-hex/rocksdb,flabby/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,vmx/rocksdb,flabby/rocksdb,hobinyoon/rocksdb,vmx/rocksdb,tsheasha/rocksdb,wenduo/rocksdb,Vaisman/rocksdb,bbiao/rocksdb,bbiao/rocksdb,bbiao/rocksdb,bbiao/rocksdb,flabby/rocksdb,tsheasha/rocksdb,wenduo/rocksdb,vmx/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,Vaisman/rocksdb,norton/rocksdb,vmx/rocksdb,OverlordQ/rocksdb,flabby/rocksdb,norton/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb