On my Linux Mint 19.1:
```bash
$ umask
0022
```

After the first run of `bitcoin-qt -sysperm=false` the `0700` permissions are expected for both the datadir (`~/.bitcoin`) and the walletdir (`~/.bitcoin/wallets`).

Actually, the directories are created with such access permissions:
```bash
$ stat ~/.bitcoin | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
$ stat ~/.bitcoin/wallets | grep Uid
Access: (0755/drwxr-xr-x)  Uid: ( 1000/ hebasto)   Gid: ( 1000/ hebasto)
```

Refs:
- #4286
- #13371
- #13389

NOTE: reading through the initial PR #4286 makes me think it was controversial. Is it a better and simpler way to just get rid of `-sysperm` option? I believe a user who needs this option can easily run `chown` command.
#endif
#ifdef USE_NATPMP
    argsman.AddArg("-natpmp", strprintf("Use NAT-PMP to map the listening port (default: %s)", DEFAULT_NATPMP ? "1 when listening and no -proxy" : "0"), ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
#else
    hidden_args.emplace_back("-natpmp");
#endif 
    argsman.AddArg("-whitebind=<[permissions@]addr>", "Bind to the given address and add permission flags to the peers connecting to it. "
        "Use [host]:port notation for IPv6. Allowed permissions: " + Join(NET_PERMISSIONS_DOC, ", ") + ". "
        "Specify multiple permissions separated by commas (default: download,noban,mempool,relay). Can be specified multiple times.", ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
    argsman.AddArg("-whitelist=<[permissions@]IP address or network>", "Add permission flags to the peers connecting from the given IP address (e.g. 1.2.3.4) or "
        "CIDR-notated network (e.g. 1.2.3.024). Uses the same permissions as "
        "-whitebind. Can be specified multiple times." , ArgsManager::ALLOW_ANY, OptionsCategory::CONNECTION);
    g_wallet_init_interface.AddWalletOptions(argsman);
#if ENABLE_ZMQ
    argsman.AddArg("-zmqpubhashblock=<address>", "Enable publish hash block in <address>", ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubhashtx=<address>", "Enable publish hash transaction in <address>", ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubrawblock=<address>", "Enable publish raw block in <address>", ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubrawtx=<address>", "Enable publish raw transaction in <address>", ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubsequence=<address>", "Enable publish hash block and tx sequence in <address>", ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubhashblockhwm=<n>", strprintf("Set publish hash block outbound message high water mark (default: %d)", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM), ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubhashtxhwm=<n>", strprintf("Set publish hash transaction outbound message high water mark (default: %d)", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM), ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubrawblockhwm=<n>", strprintf("Set publish raw block outbound message high water mark (default: %d)", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM), ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubrawtxhwm=<n>", strprintf("Set publish raw transaction outbound message high water mark (default: %d)", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM), ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
    argsman.AddArg("-zmqpubsequencehwm=<n>", strprintf("Set publish hash sequence message high water mark (default: %d)", CZMQAbstractNotifier::DEFAULT_ZMQ_SNDHWM), ArgsManager::ALLOW_ANY, OptionsCategory::ZMQ);
#else
    hidden_args.emplace_back("-zmqpubhashblock=<address>");
    hidden_args.emplace_back("-zmqpubhashtx=<address>");
    hidden_args.emplace_back("-zmqpubrawblock=<address>");
    hidden_args.emplace_back("-zmqpubrawtx=<address>");
    hidden_args.emplace_back("-zmqpubsequence=<n>");