Should accept positional arguments after flags

[nagisa]

Consider a command line invocation like this:

python x.py test --stage 1 --target=x86_64-unknown-linux-gnu 

It has the most commonly edited arguments somewhere middle in the command line, and the least edited – on the sides. Instead I would, so editing the command would be very quick:

python x.py --target=x86_64-unknown-linux-gnu --stage 1 test

but it fails with an error:

unknown command: --stage
Usage: x.py --stage [options] [<args>...]

(unrelatedly, it seems like its usage is also kinda wrong)

[CleanCut]

If my PR is accepted, then this is fixed. ;-)

[Mark-Simulacrum]

Based on testing today, this is fixed -- closing.

[CleanCut]

:-)