Creating a .Net standard2.0 project that also has Android references seems to create unnecessary transient dependencies

Description

Creating a .Net standard2.0 project that also has Android references to Xamarin.Android.Support.v7.AppCompatseems to create an unnecessary transient dependency toXamarin.Android.Support.v7.AppCompat`.

The .Net standard project references Microsoft.Identity.Client which only has a reference to Xamarin.Android.Support.v7.AppCompat in the MonoAndroid version of the assembly yet dotnet restore seems to try and restore that package.

Repro steps

I created a repo here: https://github.com/7sharp9/paket-mobile-test

clone https://github.com/7sharp9/paket-mobile-test
cd paket-mobile-test
dotnet restore Core

Expected behavior

dotnet restore Core works successfully

Actual behavior

dotnet restore Core fails with

dotnet restore Core                                                                                                                                                
  Restoring packages for /Users/dave.thomas/Documents/paket-mobile-test/Core/Core.fsproj...
/Users/dave.thomas/Documents/paket-mobile-test/Core/Core.fsproj : error NU1202: Package Xamarin.Android.Support.v7.AppCompat 25.4.0.2 is not compatible with netstandard2.0 (.NETStandard,Version=v2.0). Package Xamarin.Android.Support.v7.AppCompat 25.4.0.2 supports: monoandroid70 (MonoAndroid,Version=v7.0)

Known workarounds

?

Clone the linked paket-mobile-test repository and run dotnet restore Core for Core/Core.fsproj to reproduce the incompatible Xamarin.Android.Support.v7.AppCompat dependency. Trace how Paket or restore selects dependencies for netstandard2.0 versus MonoAndroid, and consider the issue done when the restore completes without attempting to restore the Android-only package.