Fix cad/kicad build with future CMake versions

[adridg]

Summary

The old modules use CMake internals that are going away in 3.11;
this particular module has been shipped with CMake since 3.0 at least,
so it's just not necessary except on silly ancient platforms.

[tcberner]

Looks good to me.

[adridg]

The same fix applies to kicad-devel; I'd just like an "ack" from the maintainer.