Major Description
The mysql_remap plugin failed to find libmysqlclient on CentOS6 and CentOS7 because this library is installed in /usr/lib/mysql rather than a default search path.
I poked around a both and I think that you are supposes to use the mysql_config tool to detect the linker flags. On CentOS7 with MariaDB, the mariadb-devel package installs this, however on CentOS6, the mysql-devel package does not install it. Both packages ship a mysql.m4 autoconf macro that uses mysql_config to do the detection.
I think the right approach here is to pull in the autoconf macro and document that building this requires mysql_config.