Fix clang compile error under Linux

util/options_sanity_check.h

@@ -23,7 +23,7 @@ enum OptionsSanityCheckLevel : unsigned char {
 
 // The sanity check level for DB options
 static const std::unordered_map<std::string, OptionsSanityCheckLevel>
-    sanity_level_db_options;
+    sanity_level_db_options {};
 
 // The sanity check level for column-family options
 static const std::unordered_map<std::string, OptionsSanityCheckLevel>
@@ -35,7 +35,7 @@ static const std::unordered_map<std::string, OptionsSanityCheckLevel>
 
 // The sanity check level for block-based table options
 static const std::unordered_map<std::string, OptionsSanityCheckLevel>
-    sanity_level_bbt_options;
+    sanity_level_bbt_options {};
 
 OptionsSanityCheckLevel DBOptionSanityCheckLevel(
     const std::string& options_name);