Don't link NetBSD programs with -ldl in linkXRayRuntimeDeps

Summary:
There is no such library on NetBSD, the corresponding functions like dlopen(3) are in libc.

Sponsored by <The NetBSD Foundation>

Reviewers: joerg, vitalybuka, eugenis

Reviewed By: vitalybuka

Subscribers: dberris, llvm-commits, #sanitizers

Tags: #sanitizers

Differential Revision: https://reviews.llvm.org/D41021

llvm-svn: 320220