libical: don't build examples

One of these fails to link in a static build. I've fixed it
upstream, but I don't think there's any value building the examples
in Nixpkgs regardless, so let's disable them.

Link: https://github.com/libical/libical/pull/932

+1
+1
pkgs/by-name/li/libical/package.nix
··· 80 80 cmakeFlags = 81 81 [ 82 82 "-DENABLE_GTK_DOC=False" 83 + "-DLIBICAL_BUILD_EXAMPLES=False" 83 84 "-DGOBJECT_INTROSPECTION=${if withIntrospection then "True" else "False"}" 84 85 "-DICAL_GLIB_VAPI=${if withIntrospection then "True" else "False"}" 85 86 ]