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.
{
    fs::path settings = GetPathArg("-settings", BITCOIN_SETTINGS_FILENAME);
    if (settings.empty()) {
        return false;
    }
    if (backup) {
        settings += ".bak";
    }
    if (filepath) {
        *filepath = fsbridge::AbsPathJoin(GetDataDirNet(), temp ? settings + ".tmp" : settings);
    }
    return true;
}
static void SaveErrors(const std::vector<std::string> errors, std::vector<std::string>* error_out)
{
    for (const auto& error : errors) {
        if (error_out) {
            error_out->emplace_back(error);
        } else {
            LogPrintf("%s\n", error);
        }
    }
}
bool ArgsManager::ReadSettingsFile(std::vector<std::string>* errors)