support dynamic bootfs partitions in fstab

extra/generic-root/etc/fstab

@@ -1,9 +1,6 @@
 ## <file system>  <mount point> <type> <options>              <dump><pass>
-## proc
-proc              /proc         proc   nodev,noexec,nosuid       0    0
-
 ## rootfs
 /dev/mmcblk0p2    /             ext4   noatime                   0    1
 
 ## bootfs
-/dev/mmcblk0p1    /boot         vfat   defaults                  0    0
+/dev/mmcblk0p1    /boot         {{{BOOTFS}}}   defaults                  0    1

lib/helpers

@@ -82,6 +82,8 @@ copy-root-overlay() {
 		notice "copying generic-root" && \
 		sudo cp -rfv $R/extra/generic-root/* $strapdir
 
+	sudo sed -e "s/{{{BOOTFS}}}/$bootfs/" -i "$strapdir/etc/fstab"
+
 	[[ -d $R/extra/$device_name ]] && \
 		notice "copying ${device_name}-root" && \
 		sudo cp -rfv $R/extra/$device_name/* $strapdir