Missing Expected Output Files

[d-sonuga]

The benchmarks in benchmarks/libsodium are missing their expected stdout and stderr files.

[jlb6740]

I believe the checker here uses the basename of the wasmfile as the basis for the filename used for stderr. This probably should change to something more generic so that we don't have a bunch of redundant stderr.expected files. In this case all benchmarks are expected to return '0' to stdout. Will confirm and work on the patch to make a default.stderr.expected and default.stdout.expected when we don't care for the distinction.