fix(toml): Ensure targets are in a deterministic order

With rust-lang#13713, we enumerate all targets in `Cargo.toml` on `cargo publish`
and `cargo vendor`.
However, the order of the targets is non-determistic.
This can be annoying for comparing the published `Cargo.toml` across releases but even
worse is the churn it causes for `cargo vendor`.

So we sort all the targets during publish.
This keeps costs minimal with the following risks
- If the non-determinism shows up in a way that affects developers
  during development
- If there is a reason the user wants to control target order for
  explicit targets

Fixes rust-lang#13988

src/cargo/util/toml/mod.rs

@@ -2777,6 +2777,8 @@ fn prepare_targets_for_publish(
         };
         prepared.push(target);
     }
+    // `unstable` should be deterministic because we enforce that `t.name` is unique
+    prepared.sort_unstable_by_key(|t| t.name.clone());
 
     if prepared.is_empty() {
         Ok(None)