The argument handling of this little tool was pretty rubbish. It had no
help and it required the filename to come first which is just strange.
This reworks it and makes things much nicer. It's still rubbish but at
least there's a chance people can figure out how to use it now.
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6607>
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