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.
if (key[0] == '/')
            key[0] = '-';
#endif
        if (key[0] != '-') {
            if (!m_accept_any_command && m_command.empty()) {
                
                std::optional<unsigned int> flags = GetArgFlags(key);
                if (!flags || !(*flags & ArgsManager::COMMAND)) {
                    error = strprintf("Invalid command '%s'", argv[i]);
                    return false;
                }
            }
            m_command.push_back(key);
            while (++i < argc) {
                
                m_command.push_back(argv[i]);
            }
            break;
        }
        
        if (key.length() > 1 && key[1] == '-')
            key.erase(0, 1);
        
        key.erase(0, 1);
        KeyInfo keyinfo = InterpretKey(key);
        std::optional<unsigned int> flags = GetArgFlags('-' + keyinfo.name);
        
        
        
        if (!flags || !keyinfo.section.empty()) {