message: Enable `--target-dir` support in `install` subcommand
diff: @@ -57,6 +57,7 @@ pub fn cli() -> App {
  "Install all examples",
  )
  .arg_target_triple("Build for the target triple")
  + .arg_target_dir()
  .arg(opt("root", "Directory to install packages into").value_name("DIR"))
  .arg(
  opt("index", "Registry index to install from")
  