message: Remove vestigial CLANG_USED_LIBS.
  The actual definition was removed 4 months ago with r294515.
diff: @@ -40,7 +40,7 @@ function(add_lldb_unittest test_name)
  POST_BUILD
  COMMAND "${CMAKE_COMMAND}" -E make_directory ${CMAKE_CURRENT_BINARY_DIR}/Inputs)
  - target_link_libraries(${test_name} ${ARG_LINK_LIBS} ${CLANG_USED_LIBS} ${LLDB_SYSTEM_LIBS})
  + target_link_libraries(${test_name} ${ARG_LINK_LIBS} ${LLDB_SYSTEM_LIBS})
  endfunction()
  function(add_unittest_inputs test_name inputs)
  