fix bootimage.cpp build regression
fix bootimage.cpp build regression

I forgot to update bootimage.cpp when I added a parameter to Machine's
constructor in d78247a.

ucdseniordesign/avian,joshuawarner32/avian,getlantern/avian,lostdj/avian,lostdj/avian,bgould/avian,MaartenR/avian,lwahlmeier/avian,minor-jason/avian,getlantern/avian,getlantern/avian,bgould/avian,minor-jason/avian,dicej/avian,minor-jason/avian,getlantern/avian,ucdseniordesign/avian,joshuawarner32/avian,joshuawarner32/avian,lwahlmeier/avian,marcinolawski/avian,bgould/avian,dicej/avian,marcinolawski/avian,lwahlmeier/avian,ucdseniordesign/avian,bigfatbrowncat/avian-pack.avian,minor-jason/avian,bgould/avian,MaartenR/avian,dicej/avian,joshuawarner32/avian,lwahlmeier/avian,lostdj/avian,marcinolawski/avian,ucdseniordesign/avian,dicej/avian,MaartenR/avian,lostdj/avian,marcinolawski/avian,bigfatbrowncat/avian-pack.avian,bigfatbrowncat/avian-pack.avian,bigfatbrowncat/avian-pack.avian,MaartenR/avian