Add a debug step to the pyre workflow

[stroxler]

The version of pyre-check-nightly that is failing to run in CI (not just for us, but also for torchx) appears to work just fine on my machine. I think I need to get in and poke around to determine what is happening.

There may be other ways to debug, but if this works and I can get an interactive shell inside the instance then that will probably be a faster way to debug.