[CMake] Make the sample program in darwin_test_archs have a symbol it needs to link.

This resolves an issue building compiler-rt using Xcode 7 that was reported on llvm-dev:

http://lists.llvm.org/pipermail/llvm-dev/2015-September/090245.html

llvm-svn: 247833
diff --git a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
index 635e4b7..9b7a028 100644
--- a/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
+++ b/compiler-rt/cmake/Modules/CompilerRTDarwinUtils.cmake
@@ -49,7 +49,7 @@
   set(archs ${ARGN})
   message(STATUS "Finding valid architectures for ${os}...")
   set(SIMPLE_CPP ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/src.cpp)
-  file(WRITE ${SIMPLE_CPP} "#include <iostream>\nint main() { return 0; }\n")
+  file(WRITE ${SIMPLE_CPP} "#include <iostream>\nint main() { std::cout << std::endl; return 0; }\n")
 
   set(os_linker_flags)
   foreach(flag ${DARWIN_${os}_LINKFLAGS})