Avoid deadlock in get_e2e_artifacts (#3500)
Avoid deadlock in get_e2e_artifacts (#3500)

You can't use `process.wait()` with pipes.

Fixes https://github.com/google/iree/issues/3499
google/iree,google/iree,iree-org/iree,iree-org/iree,google/iree,iree-org/iree,google/iree,google/iree,iree-org/iree,google/iree,iree-org/iree,iree-org/iree,iree-org/iree,google/iree