FYI, this flag is used to request build arguments for linking against the embedded MySQL server library.
That library was removed in MySQL 8.0: https://mysqlserverteam.com/mysql-8-0-retiring-support-for-libmysqld/ MariaDB still supports it, and there's a separate package called libmariadbd containing it. However, mariadb_config doesn't support getting the corresponding build flags. If Amarok can work without the embedded MySQL server, I think a quick fix would be to remove the check for libmysqldbd/libmariadbd. Otherwise, the cmake find script needs to be patched.
