message: test suite: be fine with warnings when running on rustc CI
diff: @@ -26,7 +26,11 @@ fn rustc_lib_path() -> PathBuf {
  fn run_tests(mode: &str, path: &str, target: &str, mut flags: Vec<String>) {
  // Some flags we always want.
  + if rustc_test_suite().is_none() {
  + // Only `-Dwarnings` on the Miri side to make the rustc toolstate management less painful.
  + // (We often get warnings when e.g. a feature gets stabilized or some lint gets added/improved.)
  flags.push("-Dwarnings -Dunused".to_owned()); // overwrite the -Aunused in compiletest-rs
  + }
  flags.push("--edition 2018".to_owned());
  if let Ok(sysroot) = std::env::var("MIRI_SYSROOT") {
  flags.push(format!("--sysroot {}", sysroot));
  