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.
error = strprintf("Invalid parameter %s", argv[i]);
            return false;
        }
        std::optional<util::SettingsValue> value = InterpretValue(keyinfo, val ? &*val : nullptr, *flags, error);
        if (!value) return false;
        m_settings.command_line_options[keyinfo.name].push_back(*value);
    }
    
    if (auto* includes = util::FindKey(m_settings.command_line_options, "includeconf")) {
        const util::SettingsSpan values{*includes};
        
        if (!values.empty()) {
            error = "-includeconf cannot be used from commandline; -includeconf=" + values.begin()->write();
            return false; 
        }
    }
    return true;
}
std::optional<unsigned int> ArgsManager::GetArgFlags(const std::string& name) const
{
    LOCK(cs_args);
    for (const auto& arg_map : m_available_args) {
        const auto search = arg_map.second.find(name);
        if (search != arg_map.second.end()) {
            return search->second.m_flags;
        }
    }
    return std::nullopt;
}
fs::path ArgsManager::GetPathArg(std::string arg, const fs::path& default_value) const