Merge topic 'update-expat'

49693fab0d cmexpat: Create expat_config.h in build within CMake itself
bea145eb25 Merge branch 'upstream-expat' into update-expat
2da34f062a expat 2021-05-23 (a28238bd)
0ac6af4457 expat: Update script to get Expat 2.4.1

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !6157