Restore testassets during build to prevent timeouts (#8038)

* Restore testassets during build to prevent timeouts
Fixes https://github.com/aspnet/AspNetCore-Internal/issues/1695

Author: pranavkm

src/Razor/Razor.Design/test/IntegrationTests/Microsoft.AspNetCore.Razor.Design.Test.csproj

@@ -61,4 +61,8 @@ namespace Microsoft.AspNetCore.Razor.Design.IntegrationTests
     </ItemGroup>
   </Target>
 
+  <Target Name="RestoreTestProjects" BeforeTargets="Restore">
+    <MSBuild Projects="..\testassets\RestoreTestProjects\RestoreTestProjects.csproj" Targets="Restore" />
+  </Target>
+
 </Project>

src/Razor/Razor.Design/test/testassets/RestoreTestProjects/RestoreTestProjects.csproj

@@ -0,0 +1,14 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>netcoreapp2.1</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\AppWithP2PReference\AppWithP2PReference.csproj" />
+    <ProjectReference Include="..\ClassLibrary\ClassLibrary.csproj" />
+    <ProjectReference Include="..\ClassLibrary2\ClassLibrary2.csproj" />
+    <ProjectReference Include="..\SimpleMvc\SimpleMvc.csproj" />
+    <ProjectReference Include="..\SimpleMvcFSharp\SimpleMvcFSharp.fsproj" />
+    <ProjectReference Include="..\SimplePages\SimplePages.csproj" />
+  </ItemGroup>
+</Project>