Building ML.NET on Windows has a new dependency

[ericstj]

System Information (please complete the following information):

• OS & Version: Win11 23H2
• ML.NET Version: main as of 3/11/2024
• .NET Version: N/A

Describe the bug When building ML.NET I now hit:

error MSB8040: Spectre-mitigated libraries are required for this project. Install them from the Visual Studio installer (Individual components tab) for any toolsets and architectures being used. Learn more: https://aka.ms/Ofhn4c 

I was able to fix this by manually installing: "Libs for Spectre" as mentioned here: https://learn.microsoft.com/en-us/cpp/build/reference/qspectre?view=msvc-160