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.
{
    
#ifdef _MSC_VER
    
    _CrtSetReportMode(_CRT_WARN, _CRTDBG_MODE_FILE);
    _CrtSetReportFile(_CRT_WARN, CreateFileA("NUL", GENERIC_WRITE, 0, nullptr, OPEN_EXISTING, 0, 0));
    
    _set_abort_behavior(0, _WRITE_ABORT_MSG | _CALL_REPORTFAULT);
#endif
#ifdef WIN32
    
    HeapSetInformation(nullptr, HeapEnableTerminationOnCorruption, nullptr, 0);
#endif
    if (!InitShutdownState()) {
        return InitError(Untranslated("Initializing wait-for-shutdown state failed."));
    }
    if (!SetupNetworking()) {
        return InitError(Untranslated("Initializing networking failed."));
    }
#ifndef WIN32
    if (!args.GetBoolArg("-sysperms", false)) {
        umask(077);
    }
    
    registerSignalHandler(SIGTERM, HandleSIGTERM);
    registerSignalHandler(SIGINT, HandleSIGTERM);