Python 3.11 on Windows prioritises registry paths over build directory

[zooba]

If you have Python 3.11 installed by the EXE installer, and then build from source and run it from the build directory, it will detect and use the installed stdlib rather than its own.

I believe this is a regression since 3.11.1, so it hasn't shipped yet. But since it only matters in a build directory, that doesn't really matter anyway.

Linked PRs

• gh-101543: Ensure Windows registry path is only used when stdlib can't be found #101544
• [3.11] gh-101543: Ensure Windows registry path is only used when stdlib can't be found (GH-101544) #101606

[zooba]

Correction, it's not a build directory, it's a normal layout. So if we've already located the stdlib, we shouldn't be adding the root path in the registry.