Teach the driver to not try to use 'lib32' multilib spellings on ARM

which doesn't use that multilib. As a consequence, fix Clang's support
for cross compiling environments that were relying on this quirk to
ensure the correct library search path ordering.

This also re-instates the new test cases from Rafael's r193528 for
cross-compiling to ARM on Ubuntu 13.10 without any of the changes to the
existing test cases (they were no longer needed).

This solution was the result of a lot of IRC debugging and trying to
understand *exactly* what quirk was being relied upon. It took some time
for me to figure out that it was the use of 'lib32' is a multilib that
was throwing a wrench in the works.

In case you are thinking that its silly to use a multilib of 'lib' at
all, entertainingly, GCC does so as well (you can see it with the
.../lib/../lib/crt1.o pattern it uses), and the 2-phase sequence of
search paths (multilib followed by non-multilib) has observable (if
dubious) consequences. =/ Yuck.

llvm-svn: 193601