Add VS2026 multi-config section and fix VS2022 statement in BUILDING.md

[ssimard2504]

Instructions to build Stellarium with Visual Studio 2022 were revised. Instructions to build Stellarium with Visual Studio 2026 were added.

Description

Instructions with VS 2022 that claim we could not use the solution file of Stellarium (Stellarium.sln) was erroneous. It has been corrected in this newly version of BUILDING.md. Instructions on how to build Stellarium with Visual Studio 2026 (released November 2025), have been added.

The main motivation of this Pull Request is to make the documentation up-to-date. There are no dependencies required for this change. Moreover it is not linked to any issue #.

Screenshots (if appropriate):

None

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• This change requires a documentation update
• Housekeeping

How Has This Been Tested?

I successfully run the procedure for building and testing Stellarium with Visual Studio 2022 and 2026 on my local Windows-based PC.

Test Configuration:
• Operating system : Windows 11 Pro, 25H2, OS build 26200.7171
• Processor : 13th Gen Intel(R) Core(TM) i7-13700K (3.40 GHz)
• Graphic Card : NVIDIA GeForce RTX 5050 Ti
• Driver : 581.80
• Display : ASUS PA329CV, 3840x2160 | 60 Hz | Highest (32-bit) | HDCP

Checklist:

• My code follows the code style of this project.
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (header file)
• I have updated the respective chapter in the Stellarium User Guide
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[github-actions]

Hello @ssimard2504!

Thank you for the suggested improvement.

[gzotti]

I have not tested these new instructions with a new build system, but it looks good as guidelines. No more objections here. Thanks!

[github-actions]

Hello @ssimard2504!

Please check the fresh version (development snapshot) of Stellarium:
https://github.com/Stellarium/stellarium-data/releases/tag/weekly-snapshot

[github-actions]

Hello @ssimard2504!

Please check the latest stable version of Stellarium:
https://github.com/Stellarium/stellarium/releases/latest