support cross builds on OS X to non-Mac targets
support cross builds on OS X to non-Mac targets

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