message: Remove rustdoc `can_add_color_process`.
diff: @@ -41,7 +41,7 @@ use crate::core::{PackageId, Target};
  use crate::util::errors::{CargoResult, CargoResultExt, Internal, ProcessError};
  use crate::util::machine_message::Message;
  use crate::util::paths;
  -use crate::util::{self, machine_message, process, ProcessBuilder};
  +use crate::util::{self, machine_message, ProcessBuilder};
  use crate::util::{internal, join_paths, profile};
  /// Indicates whether an object is for the host architcture or the target architecture.
  @@ -636,12 +636,7 @@ fn rustdoc<'a, 'cfg>(cx: &mut Context<'a, 'cfg>, unit: &Unit<'a>) -> CargoResult
  rustdoc.arg("--crate-name").arg(&unit.target.crate_name());
  add_path_args(bcx, unit, &mut rustdoc);
  add_cap_lints(bcx, unit, &mut rustdoc);
  -
  - let mut can_add_color_process = process(&*bcx.config.rustdoc()?);
  - can_add_color_process.args(&["--color", "never", "-V"]);
  - if bcx.rustc.cached_success(&can_add_color_process)? {
  add_color(bcx, &mut rustdoc);
  - }
  if unit.kind != Kind::Host {
  if let Some(ref target) = bcx.build_config.requested_target {
  