build: Add make optimising for size optional

Signed-off-by: Bart Kuivenhoven <bemkuivenhoven@gmail.com>
arch: irq: Fix stack corruption issue

Look here for more information:

http://forum.osdev.org/viewtopic.php?f=13&t=26949

Signed-off-by: Bart Kuivenhoven <bemkuivenhoven@gmail.com>