tidy: Clean up argument handling
tidy: Clean up argument handling

Use `.nth(n)` rather than `.skip(n).next()` (also fixes a clippy
warning), and use `.into()` and a type signature rather than
`PathBuf::from`.

graydon/rust,graydon/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,aidancully/rust,aidancully/rust,GBGamer/rust,GBGamer/rust,GBGamer/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust