Remove hard-coded shell info to use the docker ENTRYPOINT instead

This lets us use the 'linux32 bash' that's specified by the i686 docker
images, without specifying it explicitly.

cibuildwheel/docker_container.py

@@ -26,22 +26,19 @@ class DockerContainer:
     bash_stdin: IO[str]
     bash_stdout: IO[str]
 
-    def __init__(self, docker_image: str, simulate_32_bit=False):
+    def __init__(self, docker_image: str):
         self.docker_image = docker_image
-        self.simulate_32_bit = simulate_32_bit
 
     def __enter__(self) -> 'DockerContainer':
         self.container_name = f'cibuildwheel-{uuid.uuid4()}'
-        shell_args = ['linux32', '/bin/bash'] if self.simulate_32_bit else ['/bin/bash']
         subprocess.run(
             [
                 'docker', 'create',
                 '--env', 'CIBUILDWHEEL',
                 '--name', self.container_name,
                 '-i',
                 '-v', '/:/host',  # ignored on CircleCI
-                self.docker_image,
-                *shell_args
+                self.docker_image
             ],
             check=True,
         )

cibuildwheel/linux.py

@@ -110,7 +110,7 @@ def build(options: BuildOptions) -> None:
             continue
 
         try:
-            with DockerContainer(docker_image, simulate_32_bit=platform_tag.endswith('i686')) as docker:
+            with DockerContainer(docker_image) as docker:
                 docker.copy_into(Path.cwd(), Path('/project'))
 
                 if options.before_all: