Add Visual Studio 2026 support

[Repiteo]

Implements baseline support for the recently released Visual Studio 2026. More advanced additions like .slnx detection/construction are not required for VS2026 to function; consequently, they're outside the scope of this PR.

Contributor Checklist:

• I have created a new test or updated the unit tests to cover the new/changed functionality.
• I have updated CHANGES.txt and RELEASE.txt (and read the README.rst).
• I have updated the appropriate documentation

[mwichmann]

Thanks for this! @bdbaddog was going to look at it over the weekend, now all he has to do is review :-)

[mwichmann]

We'll want to integrate this into CI, but at the moment support is not available. We can track actions/runner-images#13291 and make a separate PR for that topic.

[bdbaddog]

Thanks for the PR!

[Delsin-Yu]

Details

For some reason, it looks like SCons is still unable to detect the CL from Visual Studio 2026 with this PR.

Never mind, I reinstalled VS2026 and it works again. I guess me desperatly switching between VS, VS-Build-Tools, and MSVC versions eventually destroyed my Visual Studio environment variables yesterday.

[mwichmann]

Never mind, I reinstalled VS2026 and it works again. I guess me desperatly switching between VS, VS-Build-Tools, and MSVC versions eventually destroyed my Visual Studio environment variables yesterday.

eh, that's been known to happen (to me, at least). Glad it's working - let us know (probably open an issue, since this is marked completed) if there are other problems.