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.
#include <nodemempool_args.h>
#include <nodemempool_persist_args.h>
#include <nodeminer.h>
#include <nodetxreconciliation.h>
#include <nodevalidation_cache_args.h>
#include <policyfeerate.h>
#include <policyfees.h>
#include <policyfees_args.h>
#include <policypolicy.h>
#include <policysettings.h>
#include <protocol.h>
#include <rpcblockchain.h>
#include <rpcregister.h>
#include <rpcserver.h>
#include <rpcutil.h>
#include <scheduler.h>
#include <scriptsigcache.h>
#include <scriptstandard.h>
#include <shutdown.h>
#include <sync.h>
#include <timedata.h>
#include <torcontrol.h>
#include <txdb.h>
#include <txmempool.h>
#include <utilasmap.h>
#include <utilcheck.h>
#include <utilmoneystr.h>
#include <utilstrencodings.h>
#include <utilstring.h>
#include <utilsyscall_sandbox.h>