crate_universe: move build-script dep to extra_deps

A crate with a build script depends on its own `build_script_build` target. That
edge was stored in `common_attrs.deps`, which `Context::workspace_member_deps()`
collects to emit crate-hub aliases — so a library crate with a build script got a
dead crate-hub alias for itself.

Move it to `common_attrs.extra_deps`, which `workspace_member_deps()` does not
read, so the self-reference no longer yields an alias. `extra_deps` holds resolved
labels, so the edge becomes a relative `:build_script_build` (same target, same
package).

Fixes #4089.

Author: ashi009

crate_universe/src/context.rs

@@ -412,7 +412,6 @@ mod test {
                 .map(|dep| (&dep.id, context.has_duplicate_workspace_member_dep_by_alias(dep)))
                 .collect::<Vec<_>>(),
             [
-                (&CrateId::new("child".to_owned(), Version::new(0, 1, 0)), false),
                 (&CrateId::new("tonic".to_owned(), Version::new(0, 4, 3)), false),
                 (&CrateId::new("tonic-build".to_owned(), Version::new(0, 4, 2)), false),
             ],

crate_universe/src/context/crate_context.rs

@@ -1,6 +1,7 @@
 //! Crate specific information embedded into [crate::context::Context] objects.
 
 use std::collections::{BTreeMap, BTreeSet};
+use std::str::FromStr;
 
 use camino::Utf8PathBuf;
 use cargo_metadata::{Node, Package, PackageId};
@@ -496,16 +497,8 @@ impl CrateContext {
 
         let build_script_attrs = if let Some(target) = build_script_target {
             // Track the build script dependency
-            common_attrs.deps.insert(
-                CrateDependency {
-                    id: current_crate_id,
-                    target: target.crate_name.clone(),
-                    alias: None,
-                    local_path: match source_annotations.get(&annotation.node.id) {
-                        Some(SourceAnnotation::Path { path }) => Some(path.clone()),
-                        _ => None,
-                    },
-                },
+            common_attrs.extra_deps.insert(
+                Label::from_str(&format!(":{}", target.crate_name)).unwrap(),
                 None,
             );