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

[Karen Arutyunov]

Hi,

> Fix incorrect filename in libmariadb/mysql/buildfile like:
>   if ($tclass == 'windows')
>   {
> -  libmariadb/def{mariadbclient}: libmariadb/in{mariadbclient_win32} \
> +  libmariadb/def{mariadbclient}: libmariadb/in{mariadbclient_win32.def} \

No that wouldn't work. It would search for prerequisite 
mariadbclient_win32.def, rather than for mariadbclient_win32.def.in, and 
fail like this:

error: no rule to update mysql\libmariadb\in{mariadbclient_win32.def}
   info: re-run with --verbose 4 for more information
   info: while applying rule version.in to update 
mysql\libmariadb\def{mariadbclient}
   info: while applying rule c.link to update mysql\liba{mariadb}
   info: while applying rule bin.lib to update mysql\lib{mariadb}
   info: while applying rule alias to update dir{mysql\}
   info: while applying rule alias to update dir{.\}
info: failed to update dir{.\}

For 'in' type the prerequisite extension defaults to the one taken from 
the target, adding '.in' (see comment for the 'in' class in 
https://git.build2.org/cgit/build2/tree/build2/target.hxx for details).

Does the existing libmariadb project (re-)build fails for you under some 
circumstances?

Best regards,
Karen