cmake SYSTEMD_HAS_PLUS examples

GreatSQL/GreatSQL cmake/systemd.cmake :57 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

percona/percona-server cmake/systemd.cmake :58 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

facebook/mysql-5.6 cmake/systemd.cmake :57 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

logicalclocks/rondb cmake/systemd.cmake :58 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

polardb/polardbx-engine cmake/systemd.cmake :57 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

mysql/mysql-server cmake/systemd.cmake :58 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

percona/percona-xtrabackup cmake/systemd.cmake :58 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")

percona/percona-xtradb-cluster cmake/systemd.cmake :58 

MESSAGE(STATUS "SYSTEMD HAS + prefix support ${SYSTEMD_HAS_PLUS}")