Add script to update librhash from upstream

Utilities/Scripts/update-librhash.bash

@@ -0,0 +1,43 @@
+#!/usr/bin/env bash
+
+set -e
+set -x
+shopt -s dotglob
+
+readonly name="librhash"
+readonly ownership="librhash upstream <kwrobot@kitware.com>"
+readonly subtree="Utilities/cmlibrhash"
+readonly repo="https://github.com/rhash/rhash.git"
+readonly tag="master"
+readonly shortlog=false
+readonly paths="
+  COPYING
+  README
+  librhash/algorithms.c
+  librhash/algorithms.h
+  librhash/byte_order.c
+  librhash/byte_order.h
+  librhash/hex.c
+  librhash/hex.h
+  librhash/md5.c
+  librhash/md5.h
+  librhash/rhash.c
+  librhash/rhash.h
+  librhash/sha1.c
+  librhash/sha1.h
+  librhash/sha256.c
+  librhash/sha256.h
+  librhash/sha512.c
+  librhash/sha512.h
+  librhash/ustd.h
+  librhash/util.h
+"
+
+extract_source () {
+    git_archive
+    pushd "${extractdir}/${name}-reduced"
+    echo "* -whitespace" > .gitattributes
+    popd
+}
+
+. "${BASH_SOURCE%/*}/update-third-party.bash"