message: define NETWORK_REACHABILITY_AVAILABLE 0 for non-Apple platforms
diff: #include "sync/impl/apple/network_reachability_observer.hpp"
  #endif
  +#else
  +
  +#define NETWORK_REACHABILITY_AVAILABLE 0
  +
  #endif // REALM_PLATFORM_APPLE
  #endif // REALM_OS_NETWORK_REACHABILITY_HPP
  