call recreate_initramfs with the argument it needs

debian/changelog

@@ -1,4 +1,4 @@
-livecd-rootfs (2.505~ppa2) bionic; urgency=medium
+livecd-rootfs (2.505~ppa3) bionic; urgency=medium
 
   * Move casper from filesystem.squashfs to installer.squashfs. 
 

live-build/ubuntu-server/hooks/032-installer-squashfs.binary

@@ -53,7 +53,7 @@ chroot $SQUASH_ROOT apt-get update
 chroot $SQUASH_ROOT apt-get -y install user-setup curtin lupin-casper
 
 # Installing casper means we need a new initramfs
-UPDATE_INITRAMFS_OPTIONS=CASPER_GENERATE_UUID=1 recreate_initramfs
+UPDATE_INITRAMFS_OPTIONS=CASPER_GENERATE_UUID=1 recreate_initramfs $SQUASH_ROOT
 
 # Don't let cloud-init run in the live session.
 touch $SQUASH_ROOT/etc/cloud/cloud-init.disabled