Ensure restic gets the correct permissions when it's updated

Yes it's weird to modify the system package like this, but it's very handy.

See also https://restic.readthedocs.io/en/stable/080_examples.html#backing-up-your-system-without-running-restic-as-root

ansible/roles/restic/files/restic-post.hook

@@ -0,0 +1,9 @@
+[Trigger]
+Operation = Upgrade
+Type = Package
+Target = restic
+
+[Action]
+Description = Set restic binary permissions
+When = PostTransaction
+Exec = /usr/share/libalpm/scripts/restic-post.sh