message: Flash LEDs when panicking
diff: // The final piece is that the entry point of our program, _start, has to call
  // `rustc_main`. That's covered by the `_start` function in the root of this
  // crate.
  +use led;
  +use timer;
  #[lang = "start"]
  -extern "C" fn start(
  - main: fn(),
  - _argc: isize,
  - _argv: *const *const u8,
  -) -> isize {
  +extern "C" fn start(main: fn(), _argc: isize, _argv: *const *const u8) -> isize {
  main();
  0
  }
  #[lang = "eh_personality"]
  -extern "C" fn eh_personality() {}
  +extern "C" fn eh_personality() {
  + circle_leds(); // TODO: Make NRF52dK specific
  +}
  +
  #[lang = "panic_fmt"]
  unsafe extern "C" fn rust_begin_unwind() {
  - loop {}
  + flash_all_leds(); // TODO: Make NRF52DK specific
  +}
  +
  +fn circle_leds() {
  + loop {
  + led::on(0);
  + timer::delay_ms(100);
  + led::off(0);
  + led::on(1);
  + timer::delay_ms(100);
  + led::off(1);
  + led::on(3);
  + timer::delay_ms(100);
  + led::off(3);
  + led::on(2);
  + timer::delay_ms(100);
  + led::off(2);
  + }
  +}
  +
  +fn flash_all_leds() {
  + loop {
  + led::on(0);
  + led::on(1);
  + led::on(2);
  + led::on(3);
  + timer::delay_ms(100);
  + led::off(0);
  + led::off(1);
  + led::off(2);
  + led::off(3);
  + timer::delay_ms(100);
  + }
  }
  