libxml2: fix CVE-2025-6021

libxml2: fix CVE-2025-6021

A flaw was found in libxml2's xmlBuildQName function, where integer
overflows in buffer size calculations can lead to a stack-based buffer
overflow. This issue can result in memory corruption or a denial
of service when processing crafted input.

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2025-6021

Upstream-patch:
https://gitlab.gnome.org/GNOME/libxml2/-/commit/17d950ae33c23f87692aa179bacedb6743f3188a

Signed-off-by: Divya Chellam <divya.chellam@windriver.com>
Signed-off-by: Steve Sakoman <steve@sakoman.com>