Imported libraries are collected as object files, because they need to
be found in Clean System Files in the same way. In the link step
(add_imported_object_files) we check if the dependency is a normal
object file or a library, and prepend -l if it is a library.
Library names starting with -l are still ignored so that you can use
import code from library "-lmysql" and import code from library "mysql_library" in the same implementation module and compile for POSIX
and Windows.