C++ build fails when configured with RDKIT_USE_BOOST_SERIALIZATION=OFF

[rvianello]

Configuration:

• RDKit Version: 2020.09.1 and current tip of the master branch
• Operating system: observed on linux, it could probably affect other OSs too.

Description:
When the cmake build is configured with the RDKIT_USE_BOOST_SERIALIZATION flag disabled, the C++ build stops with an error inside Code/GraphMol/ScaffoldNetwork that starts with the output below (some conditional compilation directives are probably missing inside ScaffoldNetwork.h).

Scanning dependencies of target ScaffoldNetwork
[ 99%] Building CXX object Code/GraphMol/ScaffoldNetwork/CMakeFiles/ScaffoldNetwork.dir/ScaffoldNetwork.cpp.o
In file included from /opt/RDKit-build/rdkit/Code/GraphMol/ScaffoldNetwork/ScaffoldNetwork.cpp:10:
/opt/RDKit-build/rdkit/Code/GraphMol/ScaffoldNetwork/ScaffoldNetwork.h:188:8: error: 'version' is not a class template
  188 | struct version<RDKit::ScaffoldNetwork::ScaffoldNetwork> {
      |        ^~~~~~~
/opt/RDKit-build/rdkit/Code/GraphMol/ScaffoldNetwork/ScaffoldNetwork.h:188:57: error: explicit specialization of non-template 'boost::serialization::version'
  188 | struct version<RDKit::ScaffoldNetwork::ScaffoldNetwork> {
      |                                                         ^
In file included from /usr/include/boost/multi_index/detail/hash_index_iterator.hpp:22,
                 from /usr/include/boost/multi_index/hashed_index.hpp:33,
                 from /usr/include/boost/graph/named_graph.hpp:18,
                 from /usr/include/boost/graph/adjacency_list.hpp:37,
                 from /opt/RDKit-build/rdkit/Code/GraphMol/ROMol.h:27,
                 from /opt/RDKit-build/rdkit/Code/GraphMol/GraphMol.h:19,
                 from /opt/RDKit-build/rdkit/Code/GraphMol/RDKitBase.h:26,
                 from /opt/RDKit-build/rdkit/Code/GraphMol/ScaffoldNetwork/detail.h:12,
                 from /opt/RDKit-build/rdkit/Code/GraphMol/ScaffoldNetwork/ScaffoldNetwork.cpp:11:
/usr/include/boost/serialization/version.hpp:36:8: error: 'boost::serialization::version' is not a template

[greglandrum]

Yeah, I found this one too. I have a PR coming soon (probably tomorrow) to clear this and one or two other build-system related things.

[rvianello]

thank you