argument: Fix cppcoreguidelines-avoid-c-arrays, modernize-use-nullptr
```
../argument.cpp:31:7: error: do not declare C-style arrays, use std::array<> instead [cppcoreguidelines-avoid-c-arrays,-warnings-as-errors]
const option ArgumentParser::options[] = {
^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:34:6: error: use nullptr [modernize-use-nullptr,-warnings-as-errors]
{0, 0, 0, 0},
^
nullptr
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:34:12: error: use nullptr [modernize-use-nullptr,-warnings-as-errors]
{0, 0, 0, 0},
^
nullptr
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:41:57: 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)))
^
/home/andrew/src/openbmc/phosphor-led-sysfs/build/../argument.cpp:49:9: error: 'auto i' can be declared as 'const auto *i' [readability-qualified-auto,-warnings-as-errors]
auto i = &options[0];
^~~~~
const auto *
```
Change-Id: I132935d52d1470b402b0077ce3ed938b654e61b7
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
2 files changed