Trying to set up a minimal CPython extension build environment

Dockerfile

FROM python:3.7-windowsservercore

ENV VS_BUILDTOOLS '\
https://download.visualstudio.microsoft.com/download/pr/11503713\
/e64d79b40219aea618ce2fe10ebd5f0d/vs_BuildTools.exe'

COPY install-vs-tools.ps1 .
RUN .\install-vs-tools.ps1

COPY hello.c .
COPY setup.py .

RUN python setup.py install
RUN python -c "import hello; hello.say('Here is some stuff...')"

hello.c

#include <stdio.h>
#include <Python.h>

static PyObject *hello_say(PyObject *self, PyObject *args)
{
    const char *msg;
    if (!PyArg_ParseTuple(args, "s", &msg))
        return NULL;
    fprintf(stdout, "Hello! %s\n", msg);
    return Py_None;
}

static PyMethodDef HelloMethods[] = {
    {"say", hello_say, METH_VARARGS, "Say stuff."},
    {NULL, NULL, 0, NULL},
};

static struct PyModuleDef hellomodule = {
    PyModuleDef_HEAD_INIT,
    "hello",
    NULL,
    -1,
    HelloMethods,
};

PyMODINIT_FUNC
PyInit_hello(void)
{
    PyObject *m = PyModule_Create(&hellomodule);
    if (!m)
        return NULL;
    return m;
}

install-vs-tools.ps1

Set-PSDebug -Trace 1

Invoke-WebRequest -Uri "$env:VS_BUILDTOOLS" -OutFile 'vs_BuildTools.exe'

Start-Process 'vs_BuildTools.exe' -Wait -ArgumentList @(
  '--add', 'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
  '--add', 'Microsoft.VisualStudio.Component.VC.CoreBuildTools',
  '--norestart',
  '--quiet')

setup.py

from distutils.core import setup, Extension
setup(
    name="hello",
    version="1.0",
    description="Hello!",
    ext_modules=[Extension("hello", sources=["hello.c"])],
)