message: also support old 'cargo miri run -- -- args' style
diff: @@ -452,14 +452,15 @@ fn phase_cargo_miri(mut args: env::Args) {
  // Check if the next argument starts with `-Zmiri`. If yes, we assume
  // this is an old-style invocation.
  if let Some(next_arg) = args.next() {
  - if next_arg.starts_with("-Zmiri") {
  + if next_arg.starts_with("-Zmiri") || next_arg == "--" {
  eprintln!(
  "WARNING: it seems like you are setting Miri's flags in `cargo miri` the old way,\n\
  i.e., by passing them after the first `--`. This style is deprecated; please set\n\
  the MIRIFLAGS environment variable instead. `cargo miri run/test` now interprets\n\
  arguments the exact same way as `cargo run/test`."
  );
  - // Old-style invocation. Turn these into MIRIFLAGS.
  + // Old-style invocation. Turn these into MIRIFLAGS, if there are any.
  + if next_arg != "--" {
  let mut miriflags = env::var("MIRIFLAGS").unwrap_or_default();
  miriflags.push(' ');
  miriflags.push_str(&next_arg);
  @@ -472,6 +473,7 @@ fn phase_cargo_miri(mut args: env::Args) {
  miriflags.push_str(&further_arg);
  }
  env::set_var("MIRIFLAGS", miriflags);
  + }
  // Pass the remaining flags to cargo.
  cmd.args(args);
  break;
  