NuGet Pack Target should have a switch for creating analyzers

[tannergooding]

Today, the NuGet.Build.Tasks.Pack.targets only supports creating tools (via the IsTool property) and lib (the default) packages.

The targets should be updated to additionally support an IsAnalyzer property which defaults the various values to support the creation of .NET Analyzers (https://docs.microsoft.com/en-us/nuget/reference/analyzers-conventions).

Ideally, there would be additional properties to also control things like the supported framework (currently dotnet is the only supported), supported architecture, and supported languages.

The current workaround is to manually set BuildOutputTargetFolder to analyzers/{framework_name}{version}/{supported_architecture}/{supported_language} where {framework_name}{version}, {supported_architecture} and {supported_language} are optional.

[mishra14]

pinging @rohit21agrawal for visibility

[jnm2]

The current workaround is to manually set BuildOutputTargetFolder to analyzers/{framework_name}{version}/{supported_architecture}/{supported_language} where {framework_name}{version}, {supported_architecture} and {supported_language} are optional.

Unfortunately BuildOutputTargetFolder is no help since the analyzer's target framework is appended to that path, and e.g. analyzers/dotnet/cs/netstandard1.3 is not a valid path according to https://docs.microsoft.com/en-us/nuget/reference/analyzers-conventions#analyzers-path-format.

@rohit21agrawal posted one workaround at #6184 (comment):

  <PropertyGroup>
    <TargetsForTfmSpecificBuildOutput>$(TargetsForTfmSpecificBuildOutput);GetMyPackageFiles</TargetsForTfmSpecificBuildOutput>
  </PropertyGroup>

  <Target Name="GetMyPackageFiles">
    <ItemGroup>
      <TfmSpecificPackageFile Include="$(OutputPath)$(AssemblyName).dll">
        <PackagePath>analyzers/dotnet/cs</PackagePath>
      </TfmSpecificPackageFile>
    </ItemGroup>
  </Target>

The .NET Compiler Platform SDK has a different approach in its analyzer project template:
https://github.com/dotnet/roslyn-sdk/blob/master/src/VisualStudio.Roslyn.SDK/Roslyn.SDK/ProjectTemplates/CSharp/Diagnostic/Analyzer/DiagnosticAnalyzer.csproj

  <PropertyGroup>
    <IncludeBuildOutput>false</IncludeBuildOutput>
  </PropertyGroup>

  <ItemGroup>
    <None Include="$(OutputPath)\$(AssemblyName).dll" Pack="true" PackagePath="analyzers/dotnet/cs" Visible="false" />
  </ItemGroup>

The analyzer projects I've seen on GitHub so far tonight seem to have gone with managing the nuspec manually.