Fix Windows CI: import build_settings.props in shadercross project

The shadercross vcxproj was missing the build_settings.props import,
so MSBuild defaulted to PlatformToolset=v100 (VS 2010) which is not
available on the GitHub Actions windows-latest runner.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: jdolan

ObjectivelyGPU.vs15/ObjectivelyGPU-shadercross.vcxproj

@@ -24,6 +24,7 @@
     <RootNamespace>ObjectivelyGPU-shadercross</RootNamespace>
   </PropertyGroup>
 
+  <Import Project="build_settings.props" />
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.Default.props" />
   <PropertyGroup>
     <ConfigurationType>Utility</ConfigurationType>