message: Only enable Secure Enclave on hardware that has it
  ... But there appears to be no way to query this beyond waiting for a tricky error message from one of the find/add APIs??? For now just use the model number of the system which of coruse is totally bogus and fragile
diff: @@ -263,7 +263,25 @@ static void check_signed() {
  se_wallet::se_wallet() : my(new detail::se_wallet_impl()) {
  detail::check_signed();
  +
  + //How to figure out of SE is available?! Totally bogus. But no other blessed way?!?!
  + char model[256];
  + size_t model_size = sizeof(model);
  + if(sysctlbyname("hw.model", model, &model_size, nullptr, 0) == 0) {
  + if(strncmp(model, "iMacPro", strlen("iMacPro")) == 0) {
  my->populate_existing_keys();
  + return;
  + }
  + unsigned int major, minor;
  + if(sscanf(model, "MacBookPro%u,%u", &major, &minor) == 2) {
  + if(major >= 13 && minor >= 2) {
  + my->populate_existing_keys();
  + return;
  + }
  + }
  + }
  +
  + FC_THROW("Secure Enclave not supported on this hardware");
  }
  se_wallet::~se_wallet() {
  