Split the Web.BindingRedirects.config file include into a conditional line

If there is no file on disk (e.g. it has never been required/generated, or it is excluded from git and you checkout a project), do not expect it to exist, and do not 'force' its inclusion.

Author: CZEMacLeod

src/MSBuild.SDK.SystemWeb/Sdk/MSBuild.SDK.SystemWeb.DefaultItems.props

@@ -9,7 +9,10 @@
   <ItemGroup Condition="'$(EnableWebFormsDefaultItems)'=='true'">
     <Content Include="Web.config" />
     <_WebConfigConfigurations Include="$(Configurations)" />
-    <None Include="@(_WebConfigConfigurations->'Web.%(Identity).config');Web.BindingRedirects.config">
+    <None Include="@(_WebConfigConfigurations->'Web.%(Identity).config')">
+      <DependentUpon>Web.config</DependentUpon>
+    </None>
+    <None Include="Web.BindingRedirects.config" Condition="EXISTS('Web.BindingRedirects.config')">
       <DependentUpon>Web.config</DependentUpon>
     </None>
     <Content Include="Web.*.config" Exclude="@(None)">