Working on "Use std::filesystem. Remove Boost Filesystem & System" #20744, I found an unfortunate [pitfall](https://github.com/bitcoin/bitcoin/pull/20744#issuecomment-946046666) -- `boost/process.hpp` depends on `boost::filesystem` when cross-compiling for Windows. It happens in Guix environment as well.

The goal of this issue is to discuss and find a solution to get rid of `boost::filesystem`.
}
                    LogPrintf("Included configuration file %s\n", conf_file_name);
                } else {
                    error = "Failed to include configuration file " + conf_file_name;
                    return false;
                }
            }
            
            conf_file_names.clear();
            add_includes(chain_id,  chain_includes);
            add_includes({},  default_includes);
            std::string chain_id_final = GetChainName();
            if (chain_id_final != chain_id) {
                
                add_includes(chain_id_final);
            }
            for (const std::string& conf_file_name : conf_file_names) {
                tfm::format(std::cerr, "warning: -includeconf cannot be used from included files; ignoring -includeconf=%s\n", conf_file_name);
            }
        }
    }
    
    gArgs.ClearPathCache();
    if (!CheckDataDirOption()) {
        error = strprintf("specified data directory \"%s\" does not exist.", GetArg("-datadir", ""));
        return false;
    }
    return true;
}
std::string ArgsManager::GetChainName() const