... the test has been adapted by Zixing to include some new CLI
functions introduced in newer version of Cargo (like `cargo add`)
Co-Authored-By: Nick Rosbrook <nick.rosbrook@canonical.com>
... it is already covered by a more comprehensive Rust full-self-build
test.
This also fixes (or avoids) the test failure caused by this Cargo
self-build test, since this rebuild test no longer works when Cargo is
included as a sub-project inside the Rust source tree.