`gpio_hal_busy_blinky` example does not work when compiled in release mode

[jounathaen]

It's debatable if it is a good example, but anyway, it doesn't work when compiled in --release mode.

[charlesbmi]

It might work with a lower optimization level for release compilation? But, as a newcomer this repository, I agree that if the gpio_hal_blinky.rs example already exists, gpio_hal_busy_blinky doesn't seem necessary.