Add support for Mach-O Core

Right now ROPgadget for `Mach-O` coredump returns nothing

```console
$ lldb ./hello
(lldb) run -s
(lldb) process save-core /tmp/mini

$ file /tmp/mini
/tmp/mini: Mach-O 64-bit x86_64 core

$ du -sh /tmp/mini
4,4G	/tmp/mini

$ ROPgadget --binary /tmp/mini
Gadgets information
============================================================

Unique gadgets found: 0
```
