It's a command line argument. The undeniably correct way to render it is with two minus signs[1] and absolutely not something non-ascii.
[1] Not strictly a hyphen, which has its own unicode point (0x2010) outside of ascii. Unicode embraced the ambiguity by calling this point (0x2d) "HYPHEN-MINUS" formally, but really its only unique typographic usage is to represent subtraction.
[1] Not strictly a hyphen, which has its own unicode point (0x2010) outside of ascii. Unicode embraced the ambiguity by calling this point (0x2d) "HYPHEN-MINUS" formally, but really its only unique typographic usage is to represent subtraction.