osbuilder: move code into tools directory

move all osbuilder files into `tools` directory to be able
to merge this into kata-containers repo.

Signed-off-by: Salvador Fuentes <salvador.fuentes@intel.com>

tools/osbuilder/initrd-builder/README.md

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+* [Creating a guest OS initrd image](#creating-a-guest-os-initrd-image)
+* [Further information](#further-information)
+
+# Kata Containers initrd image generation
+
+A Kata Containers initrd image is generated using the `initrd_builder.sh` script.
+This script uses a rootfs directory created by the `rootfs-builder/rootfs.sh` script.
+
+## Creating a guest OS initrd image
+
+To create a guest OS initrd image run:
+
+```
+$ sudo ./initrd_builder.sh path/to/rootfs
+```
+
+The `rootfs.sh` script populates the `path/to/rootfs` directory.
+
+## Further information
+
+For more information on how to use the `initrd_builder.sh` script, run:
+
+```
+$ ./initrd_builder.sh -h
+```

tools/osbuilder/initrd-builder/initrd_builder.sh

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+#!/bin/bash
+#
+# Copyright (c) 2018 HyperHQ Inc.
+#
+# SPDX-License-Identifier: Apache-2.0
+
+set -e
+
+[ -n "$DEBUG" ] && set -x
+
+script_name="${0##*/}"
+script_dir="$(dirname $(readlink -f $0))"
+
+lib_file="${script_dir}/../scripts/lib.sh"
+source "$lib_file"
+
+INITRD_IMAGE="${INITRD_IMAGE:-kata-containers-initrd.img}"
+AGENT_BIN=${AGENT_BIN:-kata-agent}
+AGENT_INIT=${AGENT_INIT:-no}
+
+usage()
+{
+	error="${1:-0}"
+	cat <<EOT
+Usage: ${script_name} [options] <rootfs-dir>
+	This script creates a Kata Containers initrd image file based on the
+	<rootfs-dir> directory.
+
+Options:
+	-h Show help
+	-o Set the path where the generated image file is stored.
+	   DEFAULT: the path stored in the environment variable INITRD_IMAGE
+
+Extra environment variables:
+	AGENT_BIN:  use it to change the expected agent binary name
+		    DEFAULT: kata-agent
+	AGENT_INIT: use kata agent as init process
+		    DEFAULT: no
+EOT
+exit "${error}"
+}
+
+while getopts "ho:" opt
+do
+	case "$opt" in
+		h)	usage ;;
+		o)	INITRD_IMAGE="${OPTARG}" ;;
+	esac
+done
+
+shift $(( $OPTIND - 1 ))
+
+ROOTFS="$1"
+
+
+[ -n "${ROOTFS}" ] || usage
+[ -d "${ROOTFS}" ] || die "${ROOTFS} is not a directory"
+
+ROOTFS=$(readlink -f ${ROOTFS})
+IMAGE_DIR=$(dirname ${INITRD_IMAGE})
+IMAGE_DIR=$(readlink -f ${IMAGE_DIR})
+IMAGE_NAME=$(basename ${INITRD_IMAGE})
+
+# The kata rootfs image expects init to be installed
+init="${ROOTFS}/sbin/init"
+[ -x "${init}" ] || [ -L ${init} ] || die "/sbin/init is not installed in ${ROOTFS}"
+OK "init is installed"
+[ "${AGENT_INIT}" == "yes" ] || [ -x "${ROOTFS}/usr/bin/${AGENT_BIN}" ] || \
+	die "/usr/bin/${AGENT_BIN} is not installed in ${ROOTFS}
+	use AGENT_BIN env variable to change the expected agent binary name"
+OK "Agent is installed"
+
+# initramfs expects /init
+ln -sf /sbin/init "${ROOTFS}/init"
+
+info "Creating ${IMAGE_DIR}/${IMAGE_NAME} based on rootfs at ${ROOTFS}"
+( cd "${ROOTFS}" && find . | cpio -H newc -o | gzip -9 ) > "${IMAGE_DIR}"/"${IMAGE_NAME}"