bpo-46028: Calculate base_executable by resolving symlinks in a venv

[zooba]

https://bugs.python.org/issue46028

[nedbat]

Is this ready to be merged?

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 Arch Linux Asan 3.x has failed when building commit 7407fe4.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/all/#builders/582/builds/912) and take a look at the build logs.
4. Check if the failure is related to this commit (7407fe4) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/all/#builders/582/builds/912

Failed tests:

• test_multiprocessing_fork

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.pablogsal-arch-x86_64.asan/build/Lib/multiprocessing/resource_tracker.py", line 209, in main
    cache[rtype].remove(name)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: '/psm_76370e0a'


Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.pablogsal-arch-x86_64.asan/build/Lib/multiprocessing/resource_tracker.py", line 209, in main
    cache[rtype].remove(name)
    ^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: '/psm_8784d823'