We've chosen to drop our default dependence on xmlrpc. Thus we disable
the corresponding CTest submission method and remove the sources for
building xmlrpc locally. Users can re-enable the method by setting the
CTEST_USE_XMLRPC option to use a system-installed xmlrpc library.
This warning appears for libtar.obj, curltest.obj, and synch_client.obj
regularly on CMake dashboard submissions from VS builds. They seem to
occur due to some kind of race condition for objects in small targets.
There is nothing wrong with the code, so this just suppresses the
warnings.