Here's the second clang-modules issue I found (with this and #99 addressed, I could build ptree_serialization as a submodule).
It refers to some archive/basic_archive details.
'''
-- a/1.77.0/src/boost_1_77_0/boost/property_tree/ptree_serialization.hpp
+++ b/1.77.0/src/boost_1_77_0/boost/property_tree/ptree_serialization.hpp
@@ -10,8 +10,8 @@
#ifndef BOOST_PROPERTY_TREE_PTREE_SERIALIZATION_HPP_INCLUDED
#define BOOST_PROPERTY_TREE_PTREE_SERIALIZATION_HPP_INCLUDED
+#include <boost/archive/basic_archive.hpp>
#include <boost/property_tree/ptree.hpp>
#include <boost/serialization/nvp.hpp>
#include <boost/serialization/collections_save_imp.hpp>
#include <boost/serialization/detail/stack_constructor.hpp>
'''