Fix the hello-world example so it works with OCI

Author: pinkwah

examples/hello_world/Containerfile

@@ -1 +1,2 @@
 FROM alpine
+RUN apk add bash

src/deploy/builder.py

@@ -123,7 +123,7 @@ async def _async_build(
 
     proc = await ctx.engine(
         pkg.build_image,
-        "/bin/bash",
+        "bash",
         "/dev/stdin",
         env=env,
         cwd=cwd,

src/deploy/engine.py

@@ -4,7 +4,6 @@
 import hashlib
 import os
 from pathlib import Path
-import sys
 from typing import Literal, Protocol, TypeAlias
 
 
@@ -71,11 +70,6 @@ async def _engine(
     volumes = volumes or []
     image_id = await _engine_ensure_image(which, image)
 
-    for src, _, kind in volumes:
-        if kind == "rw":
-            print("Creating directory", src)
-            Path(src).mkdir(parents=True, exist_ok=True)
-
     stdin = None
     if input is not None:
         stdin = PIPE
@@ -156,7 +150,7 @@ async def _native(
 
 def get_engine(preference: EngineName | None = None) -> Engine:
     if preference is None:
-        preference = "docker" if sys.platform == "darwin" else "podman"
+        preference = "podman"
 
     match preference:
         case "podman":