Ensure we deploy the build hosts in Roslyn.VisualStudio.Setup

Without this, Microsoft.CodeAnalysis.Workspaces.MSBuild.dll itself is
deployed, but will fail to work since it can't find any build hosts
deployed alongside the DLL.

Fixes #73854

Author: jasonmalinowski

src/VisualStudio/Setup/Roslyn.VisualStudio.Setup.csproj

@@ -168,7 +168,8 @@
     </ProjectReference>
     <ProjectReference Include="..\..\Workspaces\Core\MSBuild\Microsoft.CodeAnalysis.Workspaces.MSBuild.csproj">
       <Name>Workspaces.MSBuild</Name>
-      <IncludeOutputGroupsInVSIX>BuiltProjectOutputGroup;SatelliteDllsProjectOutputGroup</IncludeOutputGroupsInVSIX>
+      <!-- Make sure we include ContentFilesProjectOutputGroup so we get the BuildHosts deployed into the VSIX -->
+      <IncludeOutputGroupsInVSIX>BuiltProjectOutputGroup;SatelliteDllsProjectOutputGroup;ContentFilesProjectOutputGroup</IncludeOutputGroupsInVSIX>
       <ForceIncludeInVSIX>true</ForceIncludeInVSIX>
       <AdditionalProperties>TargetFramework=net472</AdditionalProperties>
       <PkgDefEntry>BindingRedirect</PkgDefEntry>