Positional arguments fail with negative numbers

[SpecificProtagonist]

Because of

argh/argh/src/lib.rs

Line 923 in f02f6b4

if next_arg.starts_with('-') && !options_ended {

positional arguments that start with a - get misinterpreted as optionals. This prevents e.g. taking numbers or filenames that start with a dash as required arguments, despite being permitted by Fuchsia's command-line tools rubric.