s390x: simplify 's390x-se-luks-gencpio' script

src/libostree/s390x-se-luks-gencpio

@@ -1,22 +1,16 @@
 #!/bin/bash
-# This script creates new initramdisk with LUKS config within
+# This script appends LUKS keys and config to initrd
 set -euo pipefail
 
-old_initrd=$1
-new_initrd=$2
-currdir=$PWD
-
-# Copying existing initramdisk
-cp ${old_initrd} ${new_initrd}
+initrd=$1
+tmpdir=$2
 
 # Appending LUKS root keys and crypttab config to the end of initrd
-workdir=$(mktemp -d -p /tmp se-initramfs-XXXXXX)
-cd ${workdir}
+cd ${tmpdir}
 mkdir -p etc/luks
 cp -f /etc/luks/* etc/luks/
 cp -f /etc/crypttab etc/
-find . -mindepth 1 | cpio --quiet -H newc -o | gzip -9 -n >> ${new_initrd}
+find . -mindepth 1 | cpio --quiet -H newc -o | gzip -9 -n >> ${initrd}
 
 # Cleanup
-cd ${currdir}
-rm -rf ${workdir}
+rm -rf etc/