[clang] add infer C++ #include models when siof is enabled

Summary:
The SIOF checker relies on the header models to detect whether `<iostream>` has
been included in source files.

Reviewed By: mbouaziz

Differential Revision: D6209904

fbshipit-source-id: a48855b

infer/src/clang/ClangCommand.ml

@@ -163,7 +163,7 @@ let with_plugin_args args =
        argv_cons "-cc1"
     |> (* It's important to place this option before other -isystem options. *)
        argv_do_if
-         Config.(cxx_infer_headers && (biabduction || bufferoverrun))
+         Config.(cxx_infer_headers && (biabduction || bufferoverrun || siof))
          (List.rev_append ["-isystem"; Config.cpp_extra_include_dir])
     |> List.rev_append
          [ "-load"