s390x: add LUKS keyfile to 'sd-boot'

This allows to use Secure Execution with LUKS encrypted boot disk,
key and cryptab are stored only in 'sd-boot' encrypted image.

Signed-off-by: Nikita Dubrovskii <nikita@linux.ibm.com>

src/libostree/s390x-se-luks-gencpio

@@ -0,0 +1,22 @@
+ #!/usr/bin/bash
+ # This script creates new initramdisk with LUKS config within
+set -euo pipefail
+
+old_initrd=$1
+new_initrd=$2
+
+# Unpacking existing initramdisk
+workdir=$(mktemp -d -p /tmp se-initramfs-XXXXXX)
+cd ${workdir}
+gzip -cd ${old_initrd} | cpio -imd --quiet
+
+# Adding LUKS root key and crypttab config
+mkdir -p etc/luks
+cp -f /etc/luks/root etc/luks/
+cp -f /etc/crypttab etc/
+
+# Creating new initramdisk image
+find . | cpio --quiet -H newc -o | gzip -9 -n >> ${new_initrd}
+
+# Cleanup
+rm -rf ${workdir}