fix: use find_library instead of assuming library extension

[denis-ismailaj]

The output library filenames are not necessarily libggml.so and libclip.so. For example, on macOS their extensions are dylib.

This change outputs libggml in the same directory as libclip, and uses find_library as a more standard way of finding the correct filenames.

[monatis]

Good. I also added a build script for Linux, similar ones can be added for other platforms.