gnu: rust-term-0.4: Don't hide package.

* gnu/packages/crates-io.scm (rust-term-0.4): [arguments] Skip build.
Add rust-kernel32-sys-0.2, rust-winapi-0.2 to cargo-inputs.
[properties]: Don't inherit field.

Signed-off-by: Efraim Flashner <efraim@flashner.co.il>