[Process/NetBSD] Add missing linkage to -lutil

Add missing linkage to fix build failure with LLD:

  ld: error: undefined symbol: kinfo_getvmmap
  >>> referenced by NativeProcessNetBSD.cpp
  >>>               NativeProcessNetBSD.cpp.o:(lldb_private::process_netbsd::NativeProcessNetBSD::PopulateMemoryRegionCache()) in archive lib/liblldbPluginProcessNetBSD.a

Differential Revision: https://reviews.llvm.org/D57193

llvm-svn: 352116