DRTVWR-418: -Wl,-no_compact_unwind switch breaks exception catching!

In a clang 64-bit compile, with that switch set in CMAKE_CXX_LINK_FLAGS, we
cannot catch any user exception. This shows up right away because TUT relies
on internal exceptions to walk through test<n>() test methods, but of course
being unable to catch any exceptions in the viewer would be just as bad.

A quick Google search turned up lots of people mentioning -no_compact_unwind
without finding any documentation about what it's supposed to be good for. But
since no tests work with it, whereas they work without it -- kill it.