Clarify expected behavior for FIXME in build/fbcode_builder/getdeps/builder.py

Summary

While reading build/fbcode_builder/getdeps/builder.py, I noticed the following FIXME:

# FIXME: What is this trying to accomplish?
# Should it fail on first or >=1 errors?

The code currently iterates over runs and invokes _run_cmd() for each entry, but I'm not sure what the intended failure handling is:

for run in runs:
    self._run_cmd(
        testpilot_args + run,
        cwd=self.build_opts.fbcode_builder_dir,
        env=env,
        use_cmd_prefix=use_cmd_prefix,
    )

I'm interested in contributing to this area and wanted to clarify the intended behavior before preparing a patch.

Should the implementation:

1. Stop immediately when the first _run_cmd() invocation returns a non-zero exit code, or
2. Execute all configured runs and report failure if one or more invocations return a non-zero exit code?

I'd be happy to work on a PR once the expected behavior is confirmed. Thanks!