mysqlcppconn: export sql_mysql_get_driver_instance on all platforms
mysqlcppconn: export sql_mysql_get_driver_instance on all platforms

It was only exported in an MSVC build before, which is a regression from
the gbuild conversion (c322d509231f9e1220fb86be68f13c5f4b135ccb).

Change-Id: I46783dc5fff5383bad8f8292c615ba8daa071cf9

JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core,JurassicWordExcel/core