[BUG] empty stdout/stderr for `exec_run` on macOS

Hi, I'm running Podman Machine on a MacBook and everything works fine except the `exec_run`, the output is always empty. Below an example which works on Linux machines:

```python
>>> import podman
>>> client = podman.PodmanClient()
>>> client.images.list()
[]
>>> client.version()
{'Platform': {'Name': 'linux/arm64/fedora-41'}, 'Components': [{'Name': 'Podman Engine', 'Version': '5.4.0-dev-234c41c80', 'Details': {'APIVersion': '5.4.0-dev-234c41c80', 'Arch': 'arm64', 'BuildTime': '2025-01-22T00:00:00Z', 'Experimental': 'false', 'GitCommit': '', 'GoVersion': 'go1.23.4', 'KernelVersion': '6.12.7-200.fc41.aarch64', 'MinAPIVersion': '4.0.0', 'Os': 'linux'}}, {'Name': 'Conmon', 'Version': 'conmon version 2.1.12, commit: ', 'Details': {'Package': 'conmon-2.1.12-3.fc41.aarch64'}}, {'Name': 'OCI Runtime (crun)', 'Version': 'crun version UNKNOWN\ncommit: b143d9ea7cfea9de44222d7fcfb7f55c21ba8060\nrundir: /run/user/501/crun\nspec: 1.0.0\n+SYSTEMD +SELINUX +APPARMOR +CAP +SECCOMP +EBPF +CRIU +LIBKRUN +WASM:wasmedge +YAJL', 'Details': {'Package': 'crun-1.19.1-1.20250121161049663014.main.23.ga2d140d.fc41.aarch64'}}], 'Version': '5.4.0-dev-234c41c80', 'ApiVersion': '1.41', 'MinAPIVersion': '1.24', 'GitCommit': '', 'GoVersion': 'go1.23.4', 'Os': 'linux', 'Arch': 'arm64', 'KernelVersion': '6.12.7-200.fc41.aarch64', 'BuildTime': '2025-01-22T00:00:00Z'}
>>> container = client.containers.create("alpine", command=["sleep", "1000"])
>>> container.start()
>>> ret, out = container.exec_run("echo 42", demux=True)
>>> ret
0
>>> out
(b'', b'')
```

Any ideas?

Start at the Python client's container.exec_run entry point and reproduce the provided Podman Machine example on macOS with demux=True. Compare its behavior with Linux and verify the fix by confirming that executing `echo 42` returns the expected stdout rather than `(b'', b'')`.

Written by the indexing model from the issue text.