build_image: disable verity on arm64
build_image: disable verity on arm64

Our current scheme injects the verity hash into a free spot in x86
kernel images. This is a bad thing to try on other types ;-)

smilart/scripts,marineam/coreos-scripts,glevand/coreos--scripts,glevand/coreos--scripts,marineam/coreos-scripts,coreos/scripts,coreos/scripts,smilart/scripts,smilart/scripts,marineam/coreos-scripts