Temporarily add text-only pkgs to allowed prebuilts

Author: dseefeld

eng/SourceBuild.Tarball.AllowedPrebuilts.targets

@@ -3,7 +3,11 @@
   <Target Name="AllowWorkInProgressPrebuilts"
           BeforeTargets="ForbidPrebuilts">
     <ItemGroup>
-      <AllowedPrebuiltPackageFile/>
+      <AllowedPrebuiltPackageFile Include="
+        $(TarballPrebuiltPackageDir)microsoft.dotnet.web.itemtemplates.5.0.2.nupkg;
+        $(TarballPrebuiltPackageDir)microsoft.dotnet.web.projecttemplates.5.0.5.0.2.nupkg;
+        $(TarballPrebuiltPackageDir)microsoft.dotnet.web.spa.projecttemplates.5.0.5.0.2.nupkg;
+        " />
     </ItemGroup>
   </Target>