Merge ~mwhudson/grub-installer:lp-1847721 into ~ubuntu-installer/grub-installer:master

[Michael Hudson-Doyle]

allow invoker to override architecture and some tweaks to make installing grub for UEFI when legacy booted work

retargeted version of https://code.launchpad.net/~mwhudson/ubuntu/+source/grub-installer/+git/grub-installer/+merge/384068

[Dimitri John Ledkov (xnox)]

Matching code for https://code.launchpad.net/~mwhudson/ubiquity/+git/ubiquity/+merge/384069

diff --git a/grub-installer b/grub-installer
index 8879dbe..2329f0e 100755
--- a/grub-installer
+++ b/grub-installer
@@ -8,11 +8,16 @@ set -e
 if [ "$1" ]; then
 	ROOT="$1"
 	chroot=chroot
+	shift
 else
 	ROOT=
 	chroot=
 fi
 
+if [ "$1" ]; then
+	ARCH="$1"
+fi
+
 . /usr/share/grub-installer/functions.sh
 . /usr/share/grub-installer/otheros.sh
 
@@ -37,7 +42,7 @@ debug () {
 	[ -z "${DEBCONF_DEBUG}" ] || log "debug: $@"
 }
 
-ARCH="$(archdetect)"
+ARCH="${ARCH:-$(archdetect)}"
 info "architecture: $ARCH"
 
 umount_dirs=
@@ -494,17 +499,7 @@ case $ARCH in
 	if [ -f /var/lib/partman/ignore_uefi ]; then
 		grub_package="grub-pc"
 	else
-		grub_package="grub-efi"
-		# Override the package choice if we can figure out the
-		# right package to use directly
-		if [ -f /sys/firmware/efi/fw_platform_size ] ; then
-			SIZE=$(cat /sys/firmware/efi/fw_platform_size)
-			if [ $SIZE -eq 64 ] ; then
-				grub_package="grub-efi-amd64-signed"
-			elif [ $SIZE -eq 32 ] ; then
-				grub_package="grub-efi-ia32"
-			fi
-		fi
+		grub_package="grub-efi-amd64-signed"
 		if [ ! -d /target/boot/efi ]; then
 			# No EFI System Partition, so presumably the partitioner
 			# believed this to be unnecessary, perhaps because we're
@@ -1094,6 +1089,10 @@ EOF
 			grub_install_params="$grub_install_params --force"
 		fi
 
+		if [ "$ARCH" = "amd64/efi" ] ; then
+		        grub_install_params="$grub_install_params --target x86_64-efi"
+                fi
+
 		CODE=0
 		case $ARCH:$grub_package in
 		    *:grub|*:grub-pc|*:grub-efi*|sparc:grub-ieee1275|ppc64el/*:grub-ieee1275)