Inherit the standard input descriptor

[hovsater]

When running shards run, you should be able to work with standard input.

Fix #550

[straight-shoota]

Awesome first contribution.

Thanks for picking this up =)

[Blacksmoke16]

In one of my projects I'm using stty to get the size of the terminal. When running via shards run I noticed it prints stty: 'standard input': Inappropriate ioctl for device to standard error, while building and running it does not.

My understanding is it should be using the same IO, so they should be equivalent? I don't think it really hurts anything so could just silence STDERR and not worry about it too.