libmariadb/CMakeFiles.txt generates broken libmysqlclient.a symlink

When WITH_MYSQLCOMPAT is defined, libmariadb/CMakeLists.txt uses a custom command to generate symlinks with the standard MySQL client filenames to point at the MariaDB client library binaries.

The command to create the symlink libmysqlclient.a has a bug, however. The first argument to create_symlink should be libmariadbclient${CMAKE_STATIC_LIBRARY_SUFFIX} rather than libmariadb${CMAKE_STATIC_LIBRARY_SUFFIX} since the static archive is libmariadbclient.a.

As things stand we end up with libmysqlclient.a pointing to the non-existent libmariadb.a.