Making the Microsoft.NET.IL.Sdk cross target. (#1972)

* making ilsdk crosstarget

* editing the comment

src/coreclr/src/.nuget/Microsoft.NET.Sdk.IL/sdk/Sdk.targets

@@ -14,7 +14,7 @@ Copyright (c) .NET Foundation. All rights reserved.
 
   <PropertyGroup>
     <MSBuildAllProjects>$(MSBuildThisFileFullPath);$(MSBuildAllProjects)</MSBuildAllProjects>
-    <LanguageTargets Condition="'$(MSBuildProjectExtension)' == '.ilproj'">$(MSBuildThisFileDirectory)..\targets\Microsoft.NET.Sdk.IL.targets</LanguageTargets>
+    <LanguageTargets Condition="'$(MSBuildProjectExtension)' == '.ilproj'">$(MSBuildThisFileDirectory)..\targets\Microsoft.NET.Sdk.IL.Common.targets</LanguageTargets>
   </PropertyGroup>
 
   <Import Project="Sdk.targets" Sdk="Microsoft.NET.Sdk" />

src/coreclr/src/.nuget/Microsoft.NET.Sdk.IL/targets/Microsoft.NET.Sdk.IL.Common.targets

+<?xml version="1.0" encoding="utf-8"?>
+<!--
+***********************************************************************************************
+Microsoft.NET.Sdk.IL.Common.targets
+Copyright (c) .NET Foundation. All rights reserved. 
+***********************************************************************************************
+-->
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  
+  <Import Condition="'$(IsCrossTargetingBuild)' != 'true'" Project="$(MSBuildThisFileDirectory)Microsoft.NET.Sdk.IL.targets" />
+  <Import Condition="'$(IsCrossTargetingBuild)' == 'true'" Project="$(MSBuildExtensionsPath)Microsoft.Common.CrossTargeting.targets" />
+
+</Project> 
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