Can't open nonexistent dir/file for write

When exporting the JSON output, if the `json` directory doesn't exist, no output is written. It *does* work when the directory exists, but the file does not (e.g. `x86.json`). Regardless of if the write succeeds, the program exits with code 0. Tested on Windows using Strawberry Perl.

```
print() on closed filehandle $fh at C:/Users/.../opcodesDB/x86.pl line 128.
```