quick and dirty fix for error on macos

[emilia-ghdt]

error was that the compiler complains about the constructor of the hash of filesystem paths to be deleted

UNTESTED!!!

[julcst]

It seems like since C++17 there is also a std::hash<> implementation for std::filesystem::path (https://en.cppreference.com/w/cpp/filesystem/path/hash). Can you test if std::unordered_set<std::filesystem::path, std::hash<std::filesystem::path>> also fixes the compiler error?