enable ld(1) guidance and deflib assertions for the illumos build
ld(1) can provide guidance about things you probably should do while linking, which is actually based on our own best practices. We should enable this in our own build, and ensure we practice what we preach.
ld(1) can also ensure that libraries are not found on default search paths (ie, that illumos libraries are only found from the proto, adjunct libraries from an adjunct, etc.) We should enable this too, which prevents numerous otherwise hairy build races.