It looks like since you wrote this (years ago) Gearman has added support for MySQL by name, so you can reference it directly rather than pointing libdrizzle at it (in fact, libdrizzle may be gone).
--mysql-host arg (=localhost) MySQL host.
--mysql-port arg (=3306) Port of server. (by default 3306)
--mysql-user arg MySQL user.
--mysql-password arg MySQL user password.
--mysql-db arg MySQL database.
--mysql-table arg (=gearman_queue) MySQL table name.