Remove the 'ToolTriple' concept from the NetBSD toolchain along with my

gross hack to provide it from my previous patch removing HostInfo. This
was enshrining (and hiding from my searches) the concept of storing and
diff-ing the host and target triples. We don't have the host triple
reliably available, so we need to merely inspect the target system. I've
changed the logic in selecting library search paths for NetBSD to match
what I provided for FreeBSD -- we include both search paths, but put the
32-bit-on-64-bit-host path first so it trumps.

NetBSD maintainers, you may want to tweak this, or feel free to ask me
to tweak it. I've left a FIXME here about the challeng I see in fixing
this properly.

llvm-svn: 148952