message: replace asl_log with os_log
diff: #if NETWORK_REACHABILITY_AVAILABLE
  -#include <asl.h>
  +#include <os/log.h>
  #include "dlfcn.h"
  using namespace realm;
  @@ -37,7 +37,7 @@ SystemConfiguration::SystemConfiguration()
  m_set_callback = (set_callback_t)dlsym(m_framework_handle, "SCNetworkReachabilitySetCallback");
  m_get_flags = (get_flags_t)dlsym(m_framework_handle, "SCNetworkReachabilityGetFlags");
  } else {
  - asl_log(nullptr, nullptr, ASL_LEVEL_WARNING, "network reachability is not available");
  + os_log_info(OS_LOG_DEFAULT, "network reachability is not available");
  }
  }
  