yocto: Tune for atom-pc, not qemux86
yocto: Tune for atom-pc, not qemux86

We really want i686 instructions, otherwise we're missing out on quite
a lot of speed.  Also, I bet this will make llvm work better.

djdeath/gnome-ostree,chergert/gnome-continuous,djdeath/gnome-ostree,vrutkovs/vrutkovs.github.io,chergert/gnome-continuous,GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,djdeath/gnome-ostree,chergert/gnome-continuous,GNOME/gnome-ostree,vrutkovs/vrutkovs.github.io,GNOME/gnome-ostree