Add general_storage partition to ostree image

Signed-off-by: Frédéric Dalleau <frederic.dalleau@collabora.co.uk>
Reviewed-by: Emanuele Aina <emanuele.aina@collabora.com>
Differential Revision: https://phabricator.apertis.org/D7593

apertis-ostree-image-uefi.yaml

@@ -47,6 +47,10 @@ actions:
       - name: system
         fs: ext4
         start: 1024M
+        end: 4096M
+      - name: general_storage
+        fs: btrfs
+        start: 4096M
         end: 100%
 
   - action: ostree-deploy