Fix to building and linking for unit tests. (This should fix the segfaulting units...

Fix to building and linking for unit tests.  (This should fix the segfaulting units in optimized-dynamic.  The problem was that the code incorrectly determined the address of one of the thread-scoped global variables, and I think it's because the same library was linked twice into the unit test in two different ways, confusing the runtime support code.)