[kde-frameworks/kitemmodels] Require virtual X for tests.

Package-Manager: portage-2.2.8-r1
[eclass] Remove environment cleanup stuff for testing.
[eclass] Remove cross compilation support that has been handled by cmake-utils for a while.
[eclass] Declare cmakeargs local.
[kde-frameworks/kservice] Move SYSCONF_INSTALL_DIR from eclass.

Package-Manager: portage-2.2.8-r1
[kde-frameworks/kauth] Move SYSCONF_INSTALL_DIR from eclass.

Package-Manager: portage-2.2.8-r1
[kde-frameworks/plasma] Move SYSCONF_INSTALL_DIR from eclass.

Package-Manager: portage-2.2.8-r1
[eclass] SYSCONF_INSTALL_DIR has been moved to packages that require it.
[eclass] Remove more legacy stuff.
[eclass] Remove unused inherit.