rapidhash: Add import script to get rapidhash v3

Utilities/Scripts/update-rapidhash.bash

@@ -0,0 +1,28 @@
+#!/usr/bin/env bash
+
+set -e
+set -x
+shopt -s dotglob
+
+readonly name="rapidhash"
+readonly ownership="rapidhash upstream <kwrobot@kitware.com>"
+readonly subtree="Utilities/cmrapidhash"
+readonly repo="https://github.com/Nicoshev/rapidhash.git"
+readonly tag="rapidhash_v3"
+readonly shortlog=false
+readonly exact_tree_match=false
+readonly paths="
+  LICENSE
+  rapidhash.h
+"
+
+extract_source () {
+    git_archive
+    pushd "${extractdir}/${name}-reduced"
+    echo "* -whitespace" > .gitattributes
+    fromdos rapidhash.h
+    chmod a-x rapidhash.h
+    popd
+}
+
+. "${BASH_SOURCE%/*}/update-third-party.bash"