Rework stdin processing in get-output
Rework stdin processing in get-output

It seems that there are some problems when trying to shove large stdin
into Proc::Async (hundreds of megabytes). Putting it into a file and
then binding the stdin should work better.

Also, add optional args to run-snippet. This should make it possible
to use --ll-exception and other things.

perl6/whateverable,perl6/whateverable,MasterDuke17/whateverable,perl6/whateverable