fix: add modloop= to cmdline, revert lz4 compression

modloop was not mounting because:
1. modloop=/boot/modloop-lts was missing from kernel cmdline
2. lz4-compressed squashfs may not be supported by Alpine initramfs

Both issues result in /lib/modules not existing and all modprobe failing.

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

iso/builder/setup-builder.sh

@@ -123,10 +123,7 @@ if [ ! -f "${HOME}/.abuild/abuild.conf" ]; then
     fi
 fi
 
-# --- mkinitfs: use lz4 compression for faster modloop builds ---
-mkdir -p /etc/mkinitfs
-grep -q 'MKSQUASHFS_OPTS' /etc/mkinitfs/mkinitfs.conf 2>/dev/null || \
-    echo 'MKSQUASHFS_OPTS="-comp lz4 -Xhc"' >> /etc/mkinitfs/mkinitfs.conf
+# NOTE: lz4 compression for modloop is disabled — Alpine initramfs may not support lz4 squashfs.
 
 echo ""
 echo "=== builder setup complete ==="