argument: Fix cppcoreguidelines-pro-bounds-array-to-pointer-decay

```
../argument.cpp:32:57: error: do not implicitly decay an array into a pointer; consider using gsl::array_view or an explicit cast instead [cppcoreguidelines-pro-bounds-array-to-pointer-decay,-warnings-as-errors]
           (option = getopt_long(argc, argv, optionstr, options, nullptr)))
                                                        ^
```

Change-Id: I0960608846c1b48318dfadc469b9936bfde02cec
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
1 file changed