add a targets to nuget package.

src/Avalonia.Native/Avalonia.Native.csproj

@@ -27,5 +27,10 @@
         <Pack>true</Pack>
         <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
       </Content>
+      <Content Include="Avalonia.Native.targets.pkg">
+        <PackagePath>build/netstandard2.0/Avalonia.Native.targets</PackagePath>
+        <Pack>true</Pack>
+        <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+      </Content>
   </ItemGroup>
 </Project>

src/Avalonia.Native/Avalonia.Native.targets.pkg

@@ -0,0 +1,9 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+    <ItemGroup>
+        <None Include="$(MSBuildThisFileDirectory)..\..\runtimes\osx-x64\native\libAvalonia.Native.OSX.dylib">
+            <Link>libAvalonia.Native.OSX.dylib</Link>
+            <CopyToOutputDirectory>PreserveNewest</CopyToOutputDirectory>
+        </None>
+    </ItemGroup>
+</Project>