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" \
     "${@}"

iso/builder/build.sh

@@ -896,11 +896,6 @@ needs_full_build() {
     [ -f "${FULL_BUILD_MARKER}" ]                                        || return 0
     [ -f "${BUILD_WORK_DIR}/binary/live/filesystem.squashfs" ]           || return 0
     [ -f "${BUILD_WORK_DIR}/live-image-amd64.hybrid.iso" ]               || return 0
-    _extra_sq=$(find "${BUILD_WORK_DIR}/binary/live" -maxdepth 1 -type f -name '*.squashfs' ! -name 'filesystem.squashfs' 2>/dev/null | head -1)
-    if [ -n "$_extra_sq" ]; then
-        echo "=== full build required: multi-squashfs live image present ==="
-        return 0
-    fi
 
     _heavy=$(find \
         "${BUILDER_DIR}/VERSIONS" \
@@ -1685,7 +1680,6 @@ run_step_sh "live-build clean" "80-lb-clean" "lb clean --all 2>&1 | tail -3"
 run_step_sh "live-build config" "81-lb-config" "lb config 2>&1 | tail -5"
 dump_memtest_debug "pre-build" "${LB_DIR}"
 run_step_sh "live-build build" "90-lb-build" "lb build 2>&1"
-split_live_squashfs_layers "${LB_DIR}"
 echo "=== enforcing canonical bootloader assets ==="
 enforce_live_build_bootloader_assets "${LB_DIR}"
 reset_live_build_stage "${LB_DIR}" "binary_checksums"