Support newer ubuntu-image validations, fixes #43

Author: longsleep

snappy/gadget/meta/gadget.yaml

@@ -4,14 +4,18 @@ volumes:
         bootloader: u-boot
         structure:
             - offset: 0
-              size: 20971520 # 20480 * 1024
               type: mbr
+              size: 446
+            - offset: 512
+              type: bare
+              size: 20971008 # 1024 * 20 * 1024 - 512
               content:
                 - image: boot-assets/boot0.bin
-                  offset: 8192 # 8 * 1024
+                  offset: 8192 # 8 * 1024 (sector 16)
                 - image: boot-assets/u-boot-with-dtb.bin
-                  offset: 19554304 # 19096 * 1024
-            - type: 0C
+                  offset: 19554304 # 19096 * 1024 (sector 38192)
+            - offset: 20971520 # 1024 * 20 * 1024
+              type: 0C
               filesystem: vfat
               filesystem-label: system-boot
               size: 128M