Mark libclang nuget as non-shipping

Author: akoeplinger

nuget/Microsoft.NETCore.Runtime.Mono.LLVM.Libclang/Microsoft.NETCore.Runtime.Mono.LLVM.Libclang.pkgproj

@@ -1,5 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project ToolsVersion="12.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+
+  <PropertyGroup>
+    <IsShipping>false</IsShipping>
+  </PropertyGroup>
+
   <Import Project="$([MSBuild]::GetPathOfFileAbove(Directory.Build.props))" />
 
   <Import Condition="'$(_packageTargetOSGroup)' != ''"  Project="$(MSBuildThisFileDirectory)runtime.$(_packageTargetOSGroup).$(MSBuildProjectName).props" />