Fix build for working with docs.rs

[ifraixedes]

docs.rs is a hosted service that publishes Rust crates documentation through the built-in Rust doc comments and are published in crates.io

The docs.rs build process fails for the 2 crates present in this repository because uplink-sys requires Go and uplink depends on uplink-sys and because the second one fails the former also fails.

Initially, the issue was related to requiring Go and it was commented that it generated this problem among others in issue #19 but after spending some time to by-pass the Go requirement for building the docs we have found other issues, so the docs.rs build failure deserved a specific issue, which is this one.

There are 2 links in the docs.rs about page that provides docs in how to customize the crate build for docs.rs, those are:

• Builds
• Metadata

And for how to modify the build docs.rs build environment refer to https://forge.rust-lang.org/docs-rs/add-dependencies.html. The build environment lives in https://github.com/rust-lang/crates-build-env

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Current progress.
@ifraixedes had a look at this as part of issue #19 before this issue existed.
You can check his specific comments #19 (comment) and #19 (comment)

He avoided requiring Go for docs.rs build copying the uplink-c library binaries for the default build target (x86_64-unknown-linux-gnu) and limiting the build to the default target but then the build crashed because libclang is missing in the build environment.

After he discovered that the build environment can be modified and created this issue to follow from that point.