When building with the `--shared` option, most functionality is kept in
`libruby.so`. Therefore also run annocheck for `libruby.so`.
Use `ARG IN_DIR` to propagate multiple files into the container instead of
`ARG FILES` in the `Dockerfile-copy`. Because the `COPY` syntax in Dockerfile
doesn't support copying the multiple files.
https://stackoverflow.com/questions/61599384/specify-multiple-files-in-arg-to-copy-in-dockerfile
Co-authored-by: Vít Ondruch <vondruch@redhat.com>