Add script to update liblzma from upstream

Utilities/Scripts/update-liblzma.bash

+#!/usr/bin/env bash
+
+set -e
+set -x
+shopt -s dotglob
+
+readonly name="liblzma"
+readonly ownership="liblzma upstream <xz-devel@tukaani.org>"
+readonly subtree="Utilities/cmliblzma"
+readonly repo="http://git.tukaani.org/xz.git"
+readonly tag="v5.0.5"
+readonly shortlog=false
+readonly paths="
+  COPYING
+  src/common/common_w32res.rc
+  src/common/sysdefs.h
+  src/common/tuklib_integer.h
+  src/liblzma/
+"
+
+extract_source () {
+    git_archive
+    pushd "${extractdir}/${name}-reduced"
+    mv src/common .
+    mv src/liblzma .
+    rmdir src
+    popd
+}
+
+. "${BASH_SOURCE%/*}/update-third-party.bash"