message: fix './miri test'
diff: @@ -24,10 +24,10 @@ fn run_tests(mode: &str, path: &str, target: &str) {
  } else {
  flags.push("-Dwarnings -Dunused".to_owned()); // overwrite the -Aunused in compiletest-rs
  }
  - if let Ok(sysroot) = std::env::var("MIRI_SYSROOT") {
  + if let Ok(sysroot) = env::var("MIRI_SYSROOT") {
  flags.push(format!("--sysroot {}", sysroot));
  }
  - if let Ok(extra_flags) = std::env::var("MIRIFLAGS") {
  + if let Ok(extra_flags) = env::var("MIRIFLAGS") {
  flags.push(extra_flags);
  }
  @@ -80,14 +80,16 @@ fn get_host() -> String {
  }
  fn get_target() -> String {
  - std::env::var("MIRI_TEST_TARGET").unwrap_or_else(|_| get_host())
  + env::var("MIRI_TEST_TARGET").unwrap_or_else(|_| get_host())
  }
  fn test_runner(_tests: &[&()]) {
  // Add a test env var to do environment communication tests.
  - std::env::set_var("MIRI_ENV_VAR_TEST", "0");
  + env::set_var("MIRI_ENV_VAR_TEST", "0");
  // Let the tests know where to store temp files (they might run for a different target, which can make this hard to find).
  - std::env::set_var("MIRI_TEMP", std::env::temp_dir());
  + env::set_var("MIRI_TEMP", env::temp_dir());
  + // Panic tests expect backtraces to be printed.
  + env::set_var("RUST_BACKTRACE", "1");
  let target = get_target();
  miri_pass("tests/run-pass", &target);
  