Rust support: Cargo.toml has to be processed

[a-ovchinnikov]

In order to make it possible to prepare a Rust package for hermetic build the following steps must be accomplished:

• Cargo should be used to vendor all dependencies of a project;
• dependencies should be vendored locked and to a specific path (with cargo vendor --offline <path>);
• output of cargo vendor should be saved to amend project's cargo.toml when building the project.