message: when MIRI_LOG is set, set RUSTC_LOG_ENTRY_EXIT
diff: @@ -155,6 +155,10 @@ fn init_early_loggers() {
  // initialize them both, and we always initialize `miri`'s first.
  let env = env_logger::Env::new().filter("MIRI_LOG").write_style("MIRI_LOG_STYLE");
  env_logger::init_from_env(env);
  + // Enable verbose entry/exit logging by default if MIRI_LOG is set.
  + if env::var_os("MIRI_LOG").is_some() && env::var_os("RUSTC_LOG_ENTRY_EXIT").is_none() {
  + env::set_var("RUSTC_LOG_ENTRY_EXIT", "1");
  + }
  // We only initialize `rustc` if the env var is set (so the user asked for it).
  // If it is not set, we avoid initializing now so that we can initialize
  // later with our custom settings, and *not* log anything for what happens before
  