message: Actually pass through the request for --color=always
diff: @@ -957,7 +957,10 @@ fn phase_runner(binary: &Path, binary_args: env::Args, phase: RunnerPhase) {
  // to emit the diagnostic structure that Cargo would consume from rustc to emit colored
  // diagnostics, and ask rustc to emit them.
  // See https://github.com/rust-lang/miri/issues/2037
  - if arg.split(',').any(|a| a == "diagnostic-rendered-ansi") {
  + // First skip over the leading `=`, then check for diagnostic-rendered-ansi in the
  + // comma-separated list
  + if suffix.strip_prefix('=').unwrap().split(',').any(|a| a == "diagnostic-rendered-ansi")
  + {
  cmd.arg("--color=always");
  }
  // But aside from remembering that colored output was requested, drop this argument.
  