ghc::filesystem v1.3.8

Changes:

• Refactoring for #78, the dynamic switching helper includes are now using __MAC_OS_X_VERSION_MIN_REQUIRED to ensure that std::filesystem is only selected on macOS if the deployment target is at least Catalina.
• Bugfix for #77, the directory_iterator and the recursive_directory_iterator had an issue with the skip_permission_denied option, that leads to the inability to skip SIP protected folders on macOS.
• Enhancement for #76, _MSVC_LANG is now used when available, additionally to __cplusplus, in the helping headers to allow them to work even when /Zc:__cplusplus is not used.
• Bugfix for #75, NTFS reparse points to mapped volumes where handled incorrect, leading to false on fs::exists or not-found-errors on fs::status. Namespaced paths are not filtered anymore.