message: add comment mentioning alternative approach
diff: @@ -397,6 +397,11 @@ fn phase_cargo_miri(mut args: env::Args) {
  setup(subcommand);
  // Invoke actual cargo for the job, but with different flags.
  + // We re-use `cargo test` and `cargo run`, which makes target and binary handling very easy but
  + // requires some extra work to make the build check-only (see all the `--emit` hacks below).
  + // <https://github.com/rust-lang/miri/pull/1540#issuecomment-693553191> describes an alternative
  + // approach that uses `cargo check`, making that part easier but target and binary handling
  + // harder.
  let miri_path = std::env::current_exe().expect("current executable path invalid");
  let cargo_cmd = match subcommand {
  MiriCommand::Test => "test",
  