[bug#35318] [PATCH] Update cargo-build-system to expand package inputs

[Ivan Petkov <ivanppetkov@gmail.com>]

Hi everyone,

Chris and I had a very productive discussion around this patch series this
evening. We discussed an alternative approach to allowing the cargo-build-system
to capture all transitive Rust crate sources without changing the established
semantics around Guix inputs and native-inputs.

The short summary is introducing crates as new arguments in the package
definition. These arguments will be expanded to include the sources of any
transitive sources when lowered to a derivation, while preserving any
other Guix inputs/native-inputs the package may wish to include.

I'll be sending an updated patch series here once I get a chance to work on
this, and I’ll elaborate on the solution with more specifics then!

Thanks,
--Ivan