fix warning for unused variable

Test Plan: compile

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D7857

db/version_set.cc

@@ -588,10 +588,10 @@ void Version::ExtendOverlappingInputs(
       assert(user_cmp->Compare(flimit, user_begin) >= 0);
     }
   }
+  int count=0;
 #endif
   int startIndex = midIndex + 1;
   int endIndex = midIndex;
-  int count = 0;
 
   // check backwards from 'mid' to lower indices
   for (int i = midIndex; i >= 0 ; i--) {