bootstrap: put the component name in the tarball temp dir path

This should not matter right now, but if we ever parallelize rustbuild
this will avoid tarball contents being merged together.

Author: pietroalbini

src/bootstrap/tarball.rs

@@ -112,7 +112,7 @@ impl<'a> Tarball<'a> {
     fn new_inner(builder: &'a Builder<'a>, component: &str, target: Option<String>) -> Self {
         let pkgname = crate::dist::pkgname(builder, component);
 
-        let mut temp_dir = builder.out.join("tmp").join("tarball");
+        let mut temp_dir = builder.out.join("tmp").join("tarball").join(component);
         if let Some(target) = &target {
             temp_dir = temp_dir.join(target);
         }