use dotnet-mergenupkg instead of NupkgMerge

Author: enricosada

appveyor.ps1

@@ -32,6 +32,10 @@ pack(gi .\FSharp.Core.Nuget\FSharp.Core.nuspec)
 pack(gi .\FSharp.Compiler.Tools.Nuget\FSharp.Compiler.Tools.nuspec)
 
 # Merge the latest known .NET Core FSharp.Core nuget package with the one we build here
-& packages\NupkgMerge.1.0.0.1\tools\NupkgMerge.exe -p FSharp.Core.Nuget\FSharp.Core.$version.nupkg -s packages\Microsoft.FSharp.Core.netcore.1.0.0-alpha-160629\Microsoft.FSharp.Core.netcore.1.0.0-alpha-160629.nupkg -o lib\release\FSharp.Core.$version.nupkg
+pushd dotnet-tools
+& dotnet restore
+& dotnet mergenupkg --source ..\FSharp.Core.Nuget\FSharp.Core.$version.nupkg --other ..\packages\Microsoft.FSharp.Core.netcore.1.0.0-alpha-160629\Microsoft.FSharp.Core.netcore.1.0.0-alpha-160629.nupkg --framework netstandard1.6
+popd
+& copy FSharp.Core.Nuget\*.nupkg lib\release
 & copy FSharp.Compiler.Tools.Nuget\*.nupkg lib\release