message: with FS access, default HashMap should work on macOS
diff: +// macOS needs FS access for its HashMap:
  +// compile-flags: -Zmiri-disable-isolation
  +
  use std::collections::{self, HashMap};
  use std::hash::{BuildHasherDefault, BuildHasher};
  @@ -18,14 +21,8 @@ fn test_map<S: BuildHasher>(mut map: HashMap<i32, i32, S>) {
  assert_eq!(map.values().fold(0, |x, y| x+y), num*(num-1)/2);
  // TODO: Test Entry API, Iterators, ...
  -
  }
  fn main() {
  - if cfg!(target_os = "macos") { // TODO: Implement libstd HashMap seeding for macOS (https://github.com/rust-lang/miri/issues/686).
  - // Until then, use a deterministic map.
  - test_map::<BuildHasherDefault<collections::hash_map::DefaultHasher>>(HashMap::default());
  - } else {
  test_map(HashMap::new());
  }
  -}
  