[BUG] When selecting a .slnf for a folder, the build task builds the base .sln file

[sdcarpenter]

Describe the Issue

When opening a folder and selecting the corresponding solution file, if you select a filtered solution file (.slnf), the default build command will run the build command on the .sln file the .slnf file references and not the filtered solution, itself.

Steps To Reproduce

1. Generate a filtered solution file (.slnf) that excludes at least one project.
2. Open a folder in VS Code and select the filtered solution file.
3. Run the default dotnet build

Expected Behavior

The default build command runs dotnet build on the filtered solution file, rather than the solution file the filtered file references.

Environment Information

• OS: macOS
• VS Code Version: 1.96.0
• C# Dev Kit Versions: 1.14.14