libtool is a build tool made primarily to make your life hell if you do anything that the libtool authors did not plan for. Like who thought it would be a good idea to silently drop unknown linker-driver flags.

It writes metadata into .la files, which are text-based adjuncts to .a files. It's meant to give you a common and portable interface to static and dynamic linking.

But libtool is written in POSIX shell, it's not part of the linker, and it is a bit of a disaster.