Fix grub divert for multilayer images

grub-probe must not be called during image build so grub is diverted. In
multilayer image the chroot is always the tip of the filesystem, so we
divert grub at the beginning of each pass and undivdert it as the end.
For flat images, it's diverted just before building the chroot and
undiverted after.

live-build/auto/build

@@ -261,14 +261,14 @@ EOF
                 chmod +x chroot/usr/bin/man
 	fi
 
-	divert_grub chroot
 	if [ -n "${PASSES}" ]; then
 		PATH="config/:$PATH" lb chroot_layered "$@"
 	else
+		divert_grub chroot
 		divert_update_initramfs
 		lb chroot "$@"
+		undivert_grub chroot
 	fi
-	undivert_grub chroot
 
 	# Let all configuration non multi-layered project here.
 	# If those are moving to a multi-layer layout, this needs to be

live-build/lb_chroot_layered

@@ -175,6 +175,10 @@ create_chroot_pass () {
 	lb chroot_devpts install ${*}
 	lb chroot_proc install ${*}
 	lb chroot_sysfs install ${*}
+
+	# grub-probe should not be called as part of an image build so divert it
+	divert_grub chroot
+
 	# We run chroot_hacks only on root layers (update-initramfs diverted)
 	if $(is_root_layer $pass); then
 		divert_update_initramfs
@@ -245,6 +249,9 @@ create_chroot_pass () {
 
 	Chroot chroot "dpkg-query -W" > chroot.packages.${pass}
 
+	# Restore grub
+	undivert_grub chroot
+
 	# Deconfiguring chroot
 	if $(is_root_layer $pass); then
 		lb chroot_archives chroot remove ${*}