mysqld --help --verbose prints random values for "debug"

$ sql/mysqld --no-defaults --verbose --help| grep "^debug "

debug                                                      

sql/mysqld --no-defaults --lc-messages-dir=./sql/share  --verbose --help|grep "^debug "

debug                                                      elib.count

sql/mysqld --no-defaults --lc-messages-dir=./sql/share  --verbose --help|grep "^debug "

debug                                                       '%s' failed '%s'

Logging: mysql-test-run.pl  --verbose-restart --force --parallel=4

vardir: /var/lib/buildbot/maria-slave/power8-vlp04-bintar-debug/build/mysql-test/var

Removing old var directory...

Creating var directory '/var/lib/buildbot/maria-slave/power8-vlp04-bintar-debug/build/mysql-test/var'...

Checking supported features...

MariaDB Version 10.1.3-MariaDB-wsrep-debug

 - skipping SSL, mysqld not compiled with SSL

Using suites: main-,archive-,binlog-,csv-,federated-,funcs_1-,funcs_2-,handler-,heap-,innodb-,innodb_fts-,innodb_zip-,maria-,multi_source-,optimizer_unfixed_bugs-,parts-,percona-,perfschema-,plugins-,roles-,rpl-,sys_vars-,unit-,vcol-,wsrep-,connect,oqgraph,sequence,spider,spider/bg,sql_discovery,metadata_lock_info,query_response_time

Collecting tests...

unknown value max-binlog-stmt-cache-size= at /var/lib/buildbot/maria-slave/power8-vlp04-bintar-debug/build/mysql-test/suite.pm line 33.