Describe the bug

After downloading Python 3.8 for Win64 and installing locally, running it and asking it to use pip to install a package such as numpy gets the 32-bit version and not the 64-bit version.

To Reproduce
Steps to reproduce the behavior:

1. Have VS 2019 installed with its default Python support.
2. Install 64-bit Python 3.8
3. Run 'Python38/python.exe -m pip install numpy'
4. Notice that it's downloaded the 32-bit version.
5. Run 'Python38/python.exe'
6. 'import numpy'

C:\Users\Lucian\Desktop\Numpy Wheels>C:\Users\Lucian\AppData\Local\Programs\Python\Python38\python.exe -m pip install numpy
Collecting numpy
  Using cached numpy-1.19.0-cp38-cp38-win32.whl (10.9 MB)
Installing collected packages: numpy
  WARNING: The script f2py.exe is installed in 'C:\Users\Lucian\AppData\Local\Programs\Python\Python38\Scripts' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
Successfully installed numpy-1.19.0

C:\Users\Lucian\Desktop\Numpy Wheels>C:\Users\Lucian\AppData\Local\Programs\Python\Python38\python.exe
Python 3.8.2 (tags/v3.8.2:7b3ab59, Feb 25 2020, 23:03:10) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import numpy
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\Lucian\AppData\Local\Programs\Python\Python38\lib\site-packages\numpy\__init__.py", line 138, in <module>
    from . import _distributor_init
  File "C:\Users\Lucian\AppData\Local\Programs\Python\Python38\lib\site-packages\numpy\_distributor_init.py", line 26, in <module>
    WinDLL(os.path.abspath(filename))
  File "C:\Users\Lucian\AppData\Local\Programs\Python\Python38\lib\ctypes\__init__.py", line 373, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: [WinError 193] %1 is not a valid Win32 application

Expected behavior
The -m pip install line should install numpy-1.19.0-cp38-cp38-win_amd64.whl

Instead, it downloads and installs numpy-1.19.0-cp38-cp38-win32.whl

If you download numpy-1.19.0-cp38-cp38-win_amd64.whl by hand and use that filename instead of just 'numpy', it will refuse to install it:

C:\Users\Lucian\Desktop\Numpy Wheels>C:\Users\Lucian\AppData\Local\Programs\Python\Python38\python.exe -m pip install numpy-1.19.0-cp38-cp38-win_amd64.whl
ERROR: numpy-1.19.0-cp38-cp38-win_amd64.whl is not a supported wheel on this platform.

Note that it is actually using the newly-installed version of pip: it will complain that I am using an outdated version of pip and suggest that I install the latest version, and when I do, it stops complaining.

The exact same commands work fine from a cygwin window or a 'cmd' window.

The same commands also work for Python 3.6 and 3.7 in a VS2019 command prompt: it is something Python 3.8-specific.