gh-149887: Install python3t.lib for GIL-enabled Windows install

[ngoldbaum]

• Issue: MSI Python 3.15 GIL-enabled distributions don't include python3t.lib #149887

[ngoldbaum]

I tested this by building the installer locally on my Windows PC. There is a python3t.lib file in an install that doesn't include the free-threaded build. I can also confirm that the venv bug is fixed as well!

[ngoldbaum]

@hugovk can I fire a buildbot run for this PR?

[hugovk]

@ngoldbaum Go ahead, no need to ask. I'm always happier to see buildbot failures addressed before merge :)

Do you know how to trigger? Either apply the label for the full set, or leave a regex comment for a subset:

https://devguide.python.org/testing/buildbots/#triggering-on-pull-requests

[ngoldbaum]

!buildbot .Windows.

[bedevere-bot]

🤖 New build scheduled with the buildbot fleet by @ngoldbaum for commit cc031de 🤖

Results will be shown at:

https://buildbot.python.org/all/#/grid?branch=refs%2Fpull%2F149900%2Fmerge

The command will test the builders whose names match following regular expression: .*Windows.*

The builders matched are:

• AMD64 Windows11 Non-Debug PR
• AMD64 Windows PGO Tailcall PR
• AMD64 Windows Server 2022 NoGIL PR
• AMD64 Windows PGO NoGIL Tailcall PR
• ARM64 Windows PR
• AMD64 Windows11 Refleaks PR
• AMD64 Windows PGO NoGIL PR
• AMD64 Windows PGO PR
• AMD64 Windows10 PR
• ARM64 Windows Non-Debug PR