sdk: .NET 4.6.1 project cannot reference a .NET Standard 1.4 project - conflicting types

Repro: https://github.com/gulbanana/repro-netstandard-httpclient These two projects were created with VS2017 RC Refresh. Neither contains any meaningful code. netstdlib builds ok, but netfxlib fails:

banana@forsyth MINGW64 /c/code/repro-netstandard-httpclient/netfxlib (master)
$ dotnet build
Microsoft (R) Build Engine version 15.1.458.808
Copyright (C) Microsoft Corporation. All rights reserved.

  netstdlib -> C:\code\repro-netstandard-httpclient\netstdlib\bin\Debug\netstandard1.4\netstdlib.dll
C:\Program Files\dotnet\sdk\1.0.0-preview4-004233\Microsoft.Common.CurrentVersion.targets(1909,5): warning MSB3243: No way to resolve conflict between "System.IO.Compression, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" and "System.IO.Compression, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089". Choosing "System.IO.Compression, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089" arbitrarily. [C:\code\repro-netstandard-httpclient\netfxlib\netfxlib.csproj]
C:\Program Files\dotnet\sdk\1.0.0-preview4-004233\Microsoft.Common.CurrentVersion.targets(1909,5): warning MSB3243: No way to resolve conflict between "System.Net.Http, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" and "System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a". Choosing "System.Net.Http, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" arbitrarily. [C:\code\repro-netstandard-httpclient\netfxlib\netfxlib.csproj]
  Consider app.config remapping of assembly "System.IO.Compression, Culture=neutral, PublicKeyToken=b77a5c561934e089" from Version "4.0.0.0" [C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\System.IO.Compression.dll] to Version "4.1.0.0" [C:\Users\banana\.nuget\packages\system.io.compression\4.1.0\ref\net46\System.IO.Compression.dll] to solve conflict and get rid of warning.
  Consider app.config remapping of assembly "System.Net.Http, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a" from Version "4.0.0.0" [C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\System.Net.Http.dll] to Version "4.1.0.0" [C:\Users\banana\.nuget\packages\system.net.http\4.1.0\ref\net46\System.Net.Http.dll] to solve conflict and get rid of warning.
Class1.cs(9,29): error CS0433: The type 'HttpClient' exists in both 'System.Net.Http, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' and 'System.Net.Http, Version=4.1.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' [C:\code\repro-netstandard-httpclient\netfxlib\netfxlib.csproj]

Warnings are present even if you don’t add a line of code to either project, and if you try to use any types from System.IO.Compression or System.Net.Http it’s an unfixable compile error.