bcm2711: Write cmdline.txt and config.txt earlier

This allows userpatches customize-image-host.sh and customize-image.sh
to customize the contents of these files.

These files are now installed in the pre_install_distribution_specific
hook, which is the latest hook that runs before customize-image-host.sh.

The root= commandline option is still written (appended) in the
pre_umount_final_image hook as before, because the filesystem UUID is
not known when cmdline.txt is first written.

config/sources/families/bcm2711.conf

@@ -237,8 +237,9 @@ function pre_umount_final_image__remove_esp() {
 }
 
 # write the default config.txt config
-function pre_umount_final_image__write_raspi_config() {
-	cat <<- EOD > "${MOUNT}"/boot/firmware/config.txt
+function pre_install_distribution_specific__write_raspi_config() {
+	mkdir -p "${SDCARD}"/boot/firmware
+	cat <<- EOD > "${SDCARD}"/boot/firmware/config.txt
 		# For more options and information see
 		# http://rptl.io/configtxt
 		# Some settings may impact device functionality. See link above for details
@@ -290,10 +291,18 @@ function pre_umount_final_image__write_raspi_config() {
 	EOD
 }
 
-function pre_umount_final_image__write_raspi_cmdline() {
-	cat <<- EOD > "${MOUNT}"/boot/firmware/cmdline.txt
-		console=serial0,115200 console=tty1 loglevel=1 root=UUID=${ROOT_PART_UUID} rootfstype=${ROOTFS_TYPE} fsck.repair=yes rootwait logo.nologo cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory
+function pre_install_distribution_specific__write_raspi_cmdline() {
+	# Write most of the commandline early, to allow customizing it
+	mkdir -p "${SDCARD}"/boot/firmware
+	cat <<- EOD > "${SDCARD}"/boot/firmware/cmdline.txt
+		console=serial0,115200 console=tty1 loglevel=1 rootfstype=${ROOTFS_TYPE} fsck.repair=yes rootwait logo.nologo cgroup_enable=cpuset cgroup_memory=1 cgroup_enable=memory
 	EOD
+}
+
+function pre_umount_final_image__write_raspi_cmdline_root() {
+	# Write the root option late, since we only know the FS UUID
+	# when the image is being created
+	sed -i "s/$/ root=UUID=${ROOT_PART_UUID}/" "${MOUNT}"/boot/firmware/cmdline.txt
 
 	if [[ "${SHOW_DEBUG}" == "yes" ]]; then
 		display_alert "Showing /boot/firmware as mounted" "bcm2711" "debug"