Move/Pin to 3.1 runtime

[MarcoRossignoli]

Pin 3.1 runtime, in this way we can have a wide integration tests available

Currently pack shows a warning

  coverlet.console -> C:\git\coverlet\src\coverlet.console\bin\Debug\netcoreapp2.2\coverlet.console.dll
  Successfully created package 'C:\git\coverlet\bin\Debug\Packages\coverlet.collector.1.1.52-g15a6388dd8.nupkg'.
C:\Program Files\dotnet\sdk\3.1.100\Sdks\NuGet.Build.Tasks.Pack\build\NuGet.Build.Tasks.Pack.targets(198,5): warning NU5127: This package does not contain a lib/ or ref/ folder, and will therefore be treated as compatible for all frameworks. Since framework specific files were found under the build/ directory for netstandard1.0, consider creating the following empty files to correctly narrow the compatibility of the package: [C:\git\coverlet\src\coverlet.collector\coverlet.collector.csproj]
C:\Program Files\dotnet\sdk\3.1.100\Sdks\NuGet.Build.Tasks.Pack\build\NuGet.Build.Tasks.Pack.targets(198,5): warning NU5127: -lib/netstandard1.0/_._ [C:\git\coverlet\src\coverlet.collector\coverlet.collector.csproj]
  Successfully created package 'C:\git\coverlet\bin\Debug\Packages\coverlet.collector.1.1.52-g15a6388dd8.snupkg'.
  Successfully created package 'C:\g

I've opened an issue on nuget repo seems a bug NuGet/Home#8941

cc: @tonerdo @petli

[MarcoRossignoli]

dotnet/sdk#3001 new behaviour I think that pack will build core project, not a great issue pack is pretty fast.

[MarcoRossignoli]

we have some integration tests done with netcoreapp2.1;netcoreapp2.2 and roll forward major is not supported by default https://github.com/dotnet/designs/blob/master/accepted/runtime-binding.md

[MarcoRossignoli]

/azp run

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Azure Pipelines successfully started running 1 pipeline(s).

[MarcoRossignoli]

/azp list

[azure-pipelines]

CI/CD Pipelines for this repository:

• tonerdo.coverlet