Reintroduce r148981 with significantly improved regression test. Now it

both actually tests what it wants to, doesn't have bogus and broken
assertions in it, and is also formatted much more cleanly and
consistently. Probably still some more that can be improved here, but
its much better.

Original commit message:
----
Try to unbreak the FreeBSD toolchain's detection of 32-bit targets
inside a 64-bit freebsd machine with the 32-bit compatibility layer
installed. The FreeBSD image always has the /usr/lib32 directory, so
test for the more concrete existence of crt1.o. Also enhance the tests
for freebsd to clarify what these trees look like and exercise the new
code.

Thanks to all the FreeBSD folks for helping me understand what caused
the failure and how we might fix it. =] That helps a lot. Also, yay
build bots.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@149011 91177308-0d34-0410-b5e6-96231b3b80d8