[packaging] libmariadb: Fix incorrect filename in mysql/buildfile

[Karen Arutyunov]

Hi,

Thanks for the bug report.

> I failed to build libmariadb with VS2017:
> LINK : fatal error LNK1104: 无法打开文件“G:\prj\odb\libmariadb-vs2017 
> \mysql\lib
> mariadb\mariadbclient.def”

This is now fixed and staged. Note that you will need both the latest 
libmariadb and build2.


Best regards,
Karen