update_chroot: do not reconfigure/rebuild the SDK's GRUB for arm64
update_chroot: do not reconfigure/rebuild the SDK's GRUB for arm64

Now built/installed under the board root instead.
See https://github.com/coreos/coreos-overlay/pull/1950

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