message: Test env isolation
diff: @@ -6,4 +6,6 @@ fn main() {
  assert_eq!(env::var("MIRI_TEST"), Err(env::VarError::NotPresent));
  env::set_var("MIRI_TEST", "the answer");
  assert_eq!(env::var("MIRI_TEST"), Ok("the answer".to_owned()));
  + // Test that miri environment is isolated when communication is disabled.
  + assert!(env::var("MIRI_ENV_VAR_TEST").is_err());
  }
  