Workaround textprof/kf5-syntax-hightlighting build failure.

(library) Qt5Network crashes in the presence of VLANs. This terminates
the build when the host build process runs applications that touch
the network -- which happens during schema validation, which is done
if the host has XmlPatters installed. Workaround by ignoring XmlPatterns.

Underlying problem (Qt5Network and VLANs) has not been addressed.

PR: 231402
Reported by: Ting-Wei Lan