message: there are less places now to keep the flags in sync
diff: @@ -54,8 +54,7 @@ pub use crate::stacked_borrows::{Borrow, Stack, Stacks, BorStackItem};
  /// set per default, for maximal validation power.
  pub fn miri_default_args() -> &'static [&'static str] {
  // The flags here should be kept in sync with what bootstrap adds when `test-miri` is
  - // set, which happens in `bootstrap/bin/rustc.rs` in the rustc sources; and also
  - // kept in sync with `xargo/build.sh` in this repo and `appveyor.yml`.
  + // set, which happens in `bootstrap/bin/rustc.rs` in the rustc sources.
  &["-Zalways-encode-mir", "-Zmir-emit-retag", "-Zmir-opt-level=0"]
  }
  