KSysguard - CGroup functionality breakage

[Ben Cooksley]

Hi all,

Recently functionality was introduced to KSysguard to allow it to
interact with Linux CGroups.

Unfortunately when this change was made the code in question used
classes/functionality that was introduced in Qt 5.15. This has had the
effect of breaking the CI system as can be observed in the following
Dependency Builds:

https://build.kde.org/job/Administration/job/Dependency%20Build%20Extragear%20kf5-qt5%20SUSEQt5.14/32/console

Could someone please take a look?

Thanks,
Ben