fix(build): skip -features flag when empty (#9871)

Fixes '400 too many arguments' error when creating privileged containers without nesting/fuse features enabled.

misc/build.func

@@ -2630,10 +2630,15 @@ build_container() {
   export DEV_MODE_DRYRUN="${DEV_MODE_DRYRUN:-false}"
 
   # Build PCT_OPTIONS as multi-line string
-  PCT_OPTIONS_STRING="  -features $FEATURES
-  -hostname $HN
+  PCT_OPTIONS_STRING="  -hostname $HN
   -tags $TAGS"
 
+  # Only add -features if FEATURES is not empty
+  if [ -n "$FEATURES" ]; then
+    PCT_OPTIONS_STRING="  -features $FEATURES
+$PCT_OPTIONS_STRING"
+  fi
+
   # Add storage if specified
   if [ -n "$SD" ]; then
     PCT_OPTIONS_STRING="$PCT_OPTIONS_STRING