make util/env_posix.cc work under mac

Summary: This diff invoves some more complicated issues in the posix environment.

Test Plan: works under mac os. will need to verify dev box.

Reviewers: dhruba

Reviewed By: dhruba

CC: leveldb

Differential Revision: https://reviews.facebook.net/D14061

table/block_based_table_reader.cc

@@ -273,7 +273,7 @@ Status BlockBasedTable::Open(const Options& options,
       auto err_msg =
         "[Warning] Encountered error while reading data from stats block " +
         s.ToString();
-      Log(rep->options.info_log, err_msg.c_str());
+      Log(rep->options.info_log, "%s", err_msg.c_str());
     }
   }