sysmocom-image: build a squashfs image as well

The /boot directory is excluded from the squashfs image only, as in that
case it is stored separately. This allows booting normal sysmocom images
as rauc slots.

recipes-apps/images/sysmocom-image.inc

@@ -9,6 +9,8 @@ require recipes-apps/images/image-manifest.inc
 
 IMAGE_ROOTFS_SIZE = "32768"
 
+IMAGE_FSTYPES += "squashfs"
+IMAGE_CMD_squashfs += "-e boot"
 
 link_uimage() {
     echo "Linking the current uImage to /boot/uImage"