Only build bootable buildd images for amd64

debian/changelog

@@ -1,5 +1,6 @@
 livecd-rootfs (2.634) UNRELEASED; urgency=medium
 
+  * Only build bootable buildd images for amd64.
   * Properly setup the chroot before using the network.
 
  -- David Krauser <david.krauser@canonical.com>  Thu, 12 Dec 2019 13:50:58 -0400

live-build/buildd/hooks/02-disk-image-uefi.binary

@@ -1,7 +1,7 @@
 #!/bin/bash -eux
 
 case $ARCH in
-    amd64|arm64|armhf)
+    amd64)
         ;;
     *)
         echo "We don't create EFI images for $ARCH."

live-build/buildd/hooks/52-linux-virtual-image.binary

@@ -4,6 +4,15 @@
 # Generate linux-virtual image
 #
 
+case $ARCH in
+    amd64)
+        ;;
+    *)
+        echo "We don't build bootable Buildd images for $ARCH."
+        exit 0
+        ;;
+esac
+
 echo "Building bootable Buildd image"
 
 IMAGE_STR="# BUILDD_IMG: This file was created/modified by the Buildd Image build process"