Check / fix nuget packing with the native parts

[gfoidl]

Don't know if it is correct, so check and potentially fix it.

[gfoidl]

Orientate on https://github.com/gfoidl/CairoSharp

https://github.com/gfoidl/CairoSharp/blob/22c59eb9465e77d441515bf807e142e729b2b8fa/source/CairoSharp/CairoSharp.csproj#L28-L34

https://github.com/gfoidl/CairoSharp/blob/22c59eb9465e77d441515bf807e142e729b2b8fa/source/CairoSharp/CairoSharp.props#L3-L7

[gfoidl]

Status

.net Core / .net Standard

Type	Status
.net Core app (win-x64)	OK
.net Core app (linux-x64)	OK
.net Core lib	OK
.net Standard lib	OK

[gfoidl]

When targeting .net Full the native libs are not copied. This point has to be addressed or circumvented. For instance that the native libs are only used when running on .net Core.

This code

using System;
using System.Reflection;
using System.Runtime.Versioning;

namespace ClassLibrary1
{
    public class Class1
    {
        public void Foo()
        {
            Console.WriteLine($"FrameworkDescription: {System.Runtime.InteropServices.RuntimeInformation.FrameworkDescription}");
            Console.WriteLine($"version: {GetNetCoreVersion()}");
            Console.WriteLine($"TargetFrameworkName: {AppContext.TargetFrameworkName}");
            Console.WriteLine($"FrameworkName: {Assembly.GetEntryAssembly()?.GetCustomAttribute<TargetFrameworkAttribute>()?.FrameworkName}");
            Console.WriteLine($"FrameworkDisplayName: {Assembly.GetEntryAssembly()?.GetCustomAttribute<TargetFrameworkAttribute>()?.FrameworkDisplayName}");
            Console.WriteLine($"{nameof(IsRunningOnDotNetCore)}: {IsRunningOnDotNetCore}");
        }
        //---------------------------------------------------------------------
        public static bool IsRunningOnDotNetCore =>
            Type.GetType("System.Runtime.Loader.AssemblyLoadContext") != null;
        //---------------------------------------------------------------------
        public static string GetNetCoreVersion()
        {
            var assembly = typeof(System.Runtime.GCSettings).GetTypeInfo().Assembly;
            var assemblyPath = assembly.CodeBase.Split(new[] { '/', '\\' }, StringSplitOptions.RemoveEmptyEntries);
            int netCoreAppIndex = Array.IndexOf(assemblyPath, "Microsoft.NETCore.App");
            if (netCoreAppIndex > 0 && netCoreAppIndex < assemblyPath.Length - 2)
                return assemblyPath[netCoreAppIndex + 1];
            return null;
        }
    }
}

produces on .net Core

FrameworkDescription: .NET Core 4.6.26020.03
version: 2.0.5
TargetFrameworkName: 
FrameworkName: .NETCoreApp,Version=v2.0
FrameworkDisplayName: 
IsRunningOnDotNetCore: True

and on .net Full (4.7.1)

FrameworkDescription: .NET Framework 4.7.2600.0
version: 
TargetFrameworkName: .NETFramework,Version=v4.7.1
FrameworkName: .NETFramework,Version=v4.7.1
FrameworkDisplayName: .NET Framework 4.7.1
IsRunningOnDotNetCore: False

So all methods either get a attribute or load a type. Hence the cleares way is the one from IsRunningOnDotNetCore, but this bears the potential disadvantage when the loaded type System.Runtime.Loader.AssemblyLoadContext is ported to .net Full or any other platform that this approach will yield wrong results. So the way via FrameworkName is clear and should be followed.

[gfoidl]

Can be closed as the circumvent was done in #40, so no problem with the nuget package exists.