Migrate test packages (#4720)

* Migrate TestPackages

* Add check for desktop available

* Revert previous change

* WIP try something for non-Windows

* Another attempt to pack properly on non-windows

* Another attempt to fix pack errors

* Remove spaces

* Another attempt to make pack work cross-platform

TestAssets/TestPackages/PackageWithFakeNativeDep/PackageWithFakeNativeDep.csproj

@@ -0,0 +1,40 @@
+<Project ToolsVersion="15.0" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <Import Project="$(MSBuildExtensionsPath)\$(MSBuildToolsVersion)\Microsoft.Common.props" />
+  
+  <PropertyGroup>
+    <TargetFramework>net45</TargetFramework>
+    <AssemblyName>PackageWithFakeNativeDep</AssemblyName>
+    <RuntimeIdentifiers>win7-x64;win7-x86;osx.10.11-x64;ubuntu.14.04-x64;ubuntu.16.04-x64;centos.7-x64;rhel.7.2-x64;debian.8-x64;fedora.23-x64;opensuse.13.2-x64;osx.10.10-x64;rhel.7-x64</RuntimeIdentifiers>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <Compile Include="**\*.cs" />
+    <EmbeddedResource Include="**\*.resx" />
+    <EmbeddedResource Include="compiler\resources\**\*" />
+    <Content Include="runtimes\**\*">
+      <PackagePath>runtimes/</PackagePath>
+      <Pack>true</Pack>
+    </Content>
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.NET.Sdk">
+      <Version>1.0.0-alpha-20161104-2</Version>
+      <PrivateAssets>All</PrivateAssets>
+    </PackageReference>
+    <PackageReference Include="NETStandard.Library">
+      <Version>1.6.0</Version>
+    </PackageReference>
+  </ItemGroup>
+
+  <ItemGroup Condition=" '$(TargetFramework)' == 'net45' ">
+    <Reference Include="System" />
+    <Reference Include="Microsoft.CSharp" />
+  </ItemGroup>
+
+  <PropertyGroup Condition=" '$(Configuration)' == 'Release' ">
+    <DefineConstants>$(DefineConstants);RELEASE</DefineConstants>
+  </PropertyGroup>
+  
+  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
+</Project>