ENH: itkexpat: Add script to import from upstream

Import version 2.7.2 to match what was last manually imported by commit
commit fbee641 (ENH: Update to expat 2.7.2 code changes,
2025-09-19).

Author: bradking

Modules/ThirdParty/Expat/UpdateFromUpstream.sh

@@ -0,0 +1,33 @@
+#!/usr/bin/env bash
+
+set -e
+set -x
+shopt -s dotglob
+
+readonly name="expat"
+readonly ownership="Expat Upstream <kwrobot@kitware.com>"
+readonly subtree="Modules/ThirdParty/Expat/src/itk$name"
+readonly repo="https://github.com/libexpat/libexpat.git"
+readonly tag="R_2_7_2"
+readonly paths="
+expat/CMakeLists.txt
+expat/ConfigureChecks.cmake
+expat/COPYING
+expat/expat_config.h.cmake
+
+expat/lib/*.h
+expat/lib/*.c
+"
+
+extract_source () {
+    git_archive
+    pushd "${extractdir}/${name}-reduced"
+    echo "* -whitespace" >> .gitattributes
+    mv expat/* .
+    rmdir expat
+    fromdos ConfigureChecks.cmake CMakeLists.txt expat_config.h.cmake
+    chmod a-x ConfigureChecks.cmake CMakeLists.txt expat_config.h.cmake
+    popd
+}
+
+. "${BASH_SOURCE%/*}/../../../Utilities/Maintenance/update-third-party.bash"