Currently JVM does not check whether the directory specified via `-XX:CRaCRestoreFrom` exists delegating that to a C/R engine:
```
$ java -XX:CRaCRestoreFrom=cr
Error (criu/image.c:577): Can't open dir cr: No such file or directory
Error (criu/crtools.c:237): Couldn't open image dir cr
```

To allow the JVM itself to read from the directory (will be needed in some planned changes) and make the error message engine-independent we should instead make the JVM perform the check.