As part of the fixes in MDEV-6284 there is a package called libmysqld-dev that contains the files libmysqld.so and libmysql.a.
In a comment to MDEV-6284 Timofey Turenko commented that he thinks that the libmysqld.so file should not be inside a -dev package. In comparison to RPM packages the libmysqld.so file is inside the mariadb-server package. Debian might require that shared libs are in separate packages, but then again it does depend on the mariadb-server package to function (because it needs errmsg.sys files, reads my.cnf, and can use all the server tools, like myisamchk). I'll look into this.
I cannot copy a solution from the MySQL packaging side, as to my knowledge MySQL in Debian does not have any libmysqld.so (https://packages.debian.org/search?searchon=contents&keywords=libmysqld.so&mode=filename&suite=unstable&arch=any) though the embedded lib is described in the MySQL.com docs (https://dev.mysql.com/doc/refman/5.5/en/libmysqld.html).
As part of the fixes in MDEV-6284 there is a package called libmysqld-dev that contains the files libmysqld.so and libmysql.a.
In a comment to MDEV-6284 Timofey Turenko commented that he thinks that the libmysqld.so file should not be inside a -dev package. In comparison to RPM packages the libmysqld.so file is inside the mariadb-server package. Debian might require that shared libs are in separate packages, but then again it does depend on the mariadb-server package to function (because it needs errmsg.sys files, reads my.cnf, and can use all the server tools, like myisamchk). I'll look into this.
I cannot copy a solution from the MySQL packaging side, as to my knowledge MySQL in Debian does not have any libmysqld.so (https://packages.debian.org/search?searchon=contents&keywords=libmysqld.so&mode=filename&suite=unstable&arch=any) though the embedded lib is described in the MySQL.com docs (https://dev.mysql.com/doc/refman/5.5/en/libmysqld.html).