bin/static-delta: Add support to sign superblock

Add signing ability to "static-delta generate" builtin.

Signed-off-by: Frédéric Danis <frederic.danis@collabora.com>

bash/ostree

@@ -1613,6 +1613,8 @@ _ostree_static_delta_generate() {
         --repo
         --set-endianness
         --to
+        --sign
+        --sign-type
     "
 
     local options_with_args_glob=$( __ostree_to_extglob "$options_with_args" )
@@ -1630,6 +1632,9 @@ _ostree_static_delta_generate() {
             COMPREPLY=( $( compgen -W "l B" -- "$cur" ) )
             return 0
             ;;
+        $options_with_args_glob )
+            return 0
+            ;;
     esac
 
     case "$cur" in