Allow libc++ to be built on systems without POSIX threads

If you're crazy enough to want this sort of thing, then add
-D_LIBCPP_HAS_NO_THREADS to your CXXFLAGS and
--param=additiona_features=libcpp-has-no-threads to your lit commnad line.

http://reviews.llvm.org/D3969

llvm-svn: 217271
diff --git a/libcxx/test/thread/macro.pass.cpp b/libcxx/test/thread/macro.pass.cpp
index 243640d..c1b1377 100644
--- a/libcxx/test/thread/macro.pass.cpp
+++ b/libcxx/test/thread/macro.pass.cpp
@@ -6,6 +6,8 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+//
+// UNSUPPORTED: libcpp-has-no-threads
 
 // <thread>