remove "field is never read" warning

src/bootstrap/lib.rs

@@ -277,7 +277,6 @@ pub struct Build {
 struct Crate {
     name: Interned<String>,
     deps: HashSet<Interned<String>>,
-    id: String,
     path: PathBuf,
 }
 

src/bootstrap/metadata.rs

@@ -14,7 +14,6 @@ struct Output {
 
 #[derive(Deserialize)]
 struct Package {
-    id: String,
     name: String,
     source: Option<String>,
     manifest_path: String,
@@ -50,7 +49,7 @@ pub fn build(build: &mut Build) {
                 .filter(|dep| dep.source.is_none())
                 .map(|dep| INTERNER.intern_string(dep.name))
                 .collect();
-            build.crates.insert(name, Crate { name, id: package.id, deps, path });
+            build.crates.insert(name, Crate { name, deps, path });
         }
     }
 }

src/tools/bump-stage0/src/main.rs

@@ -196,7 +196,6 @@ struct ManifestPackage {
 
 #[derive(Debug, serde::Deserialize)]
 struct ManifestTargetPackage {
-    available: bool,
     url: Option<String>,
     hash: Option<String>,
     xz_url: Option<String>,