The skip-reason only cites Qt/X11. Convert the #ifdef into a platform
name check instead. The test also fails with the offscreen plugin, so
skip it for that as well.
Pick-to: 6.2
Change-Id: I49607b89f4b32359e81e1d9aadff2c3e03035c53
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Richard Moe Gustavsen <richard.gustavsen@qt.io>