mark hardfault handler as not returning

Author: jepler

ports/raspberrypi/supervisor/port.c

@@ -572,7 +572,7 @@ void port_idle_until_interrupt(void) {
 /**
  * \brief Default interrupt handler for unused IRQs.
  */
-extern void isr_hardfault(void); // provide a prototype to avoid a missing-prototypes diagnostic
+extern NORETURN void isr_hardfault(void); // provide a prototype to avoid a missing-prototypes diagnostic
 __attribute__((used)) void __not_in_flash_func(isr_hardfault)(void) {
     // Only safe mode from core 0 which is running CircuitPython. Core 1 faulting
     // should not be fatal to CP. (Fingers crossed.)