Why would you try to include QMYSQLDriver?

For MySQL plugin to work you need:
1. MySQL client library called "mysqlclient"
2. Qt MySQL plugin which either is already built and ready or to build it you need:
a) Qt source code
b) MySQL development files (headers)
c) MySQL client library (called "mysqlclient")

... and possibly dependencies of any of those. In addition to that if you run Windows you need to make sure you build the plugin in the appropriate mode (debug vs release).