Run spec tests in parallel to reduce the execution time

[stevenfontanella]

Reduces runtime from ~15 minutes to 1.5 minutes on my machine

Before:

After:

Failed test example (stdout and stderr isn't ordered with the exception unfortunately, but it's easy to re-run the particular test):

• Run tests through a thread pool with os.cpu_count() * 2 threads
  • os.cpu_count() * 4 shows no benefit. os.cpu_count() or os.cpu_count() // 2 also show no regression in runtime, but might be worse for machines with less cores. There are currently 315 spec tests total for reference.
• Prefixes round-trip file name tests with their test name to avoid clobbering the a.wasm / ab.wast files during tests
• Add stdout and stderr params to functions that print so that lines can be captured by each thread and not interleaved
  • Note that we pass stdout as the stderr param in practice so that they are interleaved, otherwise all stdout lines and stderr lines will be outputted together in each test.

[tlively]

The alpine builder has been running for over three hours now, so I think there's a problem here. Looking at the log, it looks much more verbose than before because the stdout from the wasm-shell commands is being printed. Maybe fixing that will make the builder go faster?

[kripken]

Nice work!

[kripken]

lgtm % open comments

[stevenfontanella]

Re:

The alpine builder has been running for over three hours now, so I think there's a problem here. Looking at the log, it looks much more verbose than before because the stdout from the wasm-shell commands is being printed. Maybe fixing that will make the builder go faster?

I changed support.run_command to not print the process's stdout and fixed the Alpine build (it's using a lower Python version and didn't have Queue.shutdown())

[stevenfontanella]

I think the CI problem is that this member isn't initialized in the default constructor of SmallVector since std::array is an aggregate type. I'm not sure why we see the breakage here and not in main or in other architectures. I'll try to re-run for now and send a PR to fix separately.

CI link

[kripken]

About the std::array initialization error, we do disable that warning a few lines above for some archs, and maybe we just need to disable it in more. gcc does seem to have many such false positives...