message: custom-profiles: for backward compatibility, allow 'doc' with a default 'inherits'
  Some packages still have old `Cargo.toml` with a `profile.doc` section
  and obviously without an 'inherits' keyword. We should not trip Cargo on
  processing their Cargo.toml files.
diff: @@ -152,6 +152,13 @@ impl Profiles {
  ..TomlProfile::default()
  },
  ),
  + (
  + "doc",
  + TomlProfile {
  + inherits: Some(String::from("dev")),
  + ..TomlProfile::default()
  + },
  + ),
  ]
  }
  