Is gh-28940 only for UNIX?

I built on Windows with default options (PCbuild\build.bat) and it looks like the frozen modules are used by default even though I am running in the source directory. (I put a printf() call in unmarshal_frozen_code().)

I also put a printf() in is_dev_env() and found that it returns 0 on this check:

    /* If dirname() is the same for both then it is a dev build. */
    if (len != _Py_find_basename(stdlib)) {
        return 0;
    }

I assume that's because the binary (in my case at least) is at PCbuild\amd64\python.exe which is not the same as my current directory (which is the repo root).