Fix lb config option name for squashfs compression options

--chroot-squashfs-options is not a valid lb_config option; the correct
name is --chroot-squashfs-compression-options. Without this fix lb config
aborts immediately, so the -no-xattrs flag (which prevents the
"unable to read xattr id index table" boot failure) was never applied.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

iso/builder/auto/config

@@ -42,4 +42,5 @@ lb config noauto \
     --debootstrap-options "--include=ca-certificates" \
     --apt-recommends false \
     --chroot-squashfs-compression-type zstd \
+    --chroot-squashfs-compression-options "-no-xattrs" \
     "${@}"