Do not ignore uniffi.toml for crates without a lib type
See https://github.com/mozilla/uniffi-rs/pull/2175/files#r1749374986. That PR added a filter on `cargo_metadata`'s `is_lib`. While it makes sense to ignore non-library targets here, `is_lib` only returns `true` if the crate has the `lib` type, but not e.g. for `staticlib`, `cdylib` etc. In that case none of the targets match and the crate's `uniffi.toml` gets ignored.
