Merge "Upgrade libxml2 to 7279d236364739a05657a8a614c15990eb08d0c6" am: 7cb4d979c3 am: 80288015e5

Original change: https://android-review.googlesource.com/c/platform/external/libxml2/+/1699085

Change-Id: I43e796d2c6106eea9ed7a2177f9aa21c3754e7fd