Add (most of) -Wextra to build system
Add (most of) -Wextra to build system

lab11/nrf5x-base,lab11/nrf5x-base,Tech4Race/nrf5x-base,Tech4Race/nrf5x-base,Tech4Race/nrf5x-base,lab11/nrf5x-base,Tech4Race/nrf5x-base,lab11/nrf5x-base