Optional (build-)dependencies missing

[robo9k]

For a crate with optional build-dependencies that are included with the "default" and their own implicit feature, deps.rs is showing:

No external dependencies! 🙌

See https://deps.rs/crate/magic-sys/0.4.1

Now granted this is a specific combination (though build-dependencies for -sys crates are common) but I did not find any other issues saying this is intentionally not supported, #71 has some overlap

For comparison:

• https://docs.rs/crate/magic-sys/0.4.1 correctly shows: build optional for the dependencies
• https://docs.rs/crate/magic-sys/0.4.1/features correctly shows dep:xyz for the features
• https://libraries.io/cargo/magic-sys/0.4.1 lists "0 dependencies", but has a section for "Build Dependencies"
• • https://libraries.io/cargo/magic-sys/0.4.1/tree?kind=build does not mention the dependencies are optional
• https://deps.dev/cargo/magic-sys/0.4.1/dependencies lists the dependencies without mentioning that they're build dependencies and optional

Since build-dependencies are used when building the crate itself and when using it as a dependency, I would have expected them to be listed (like the dev-dependencies are)
Since optional dependencies can be included by user choice / feature, I would also have expected them to be listed