Improve packing

[carlossanlop]

Follow up for the feedback left in https://github.com/dotnet/maintenance-packages/pull/65

• Need to evaluate IsSourceProjectPackable in Directory.Build.props, not in targets, as it was too late.
• The official yml only needs one leg to build and publish. The build linux one and the linux packing ones are unnecessary.

[ViktorHofer]

Looks good. You can revert all the project file changes and remove the new stuff in Directory.Build.props. What remains is to be able to only build the sources without the test for that packaging leg. Right now tests are built and packed:

Successfully created package '/__w/1/s/artifacts/packages/Release/NonShipping/System.Reflection.DispatchProxy.Tests.1.0.0-ci.24168.1.nupkg'.

[carlossanlop]

With the latest commits, which pass the global property /p:Test=false in the packing leg for PRs, we're no longer creating nupkgs for the test projects: https://dev.azure.com/dnceng-public/public/_build/results?buildId=607838&view=logs&j=60dbaa24-68a7-5962-8c66-270b428b4658&t=0f846b6f-8d8e-592b-9ef5-850ae44e3537

The official run should still be able to generate the package if we set <IsPackable>true</IsPackable> in a csproj (tested locally).

[ViktorHofer]

which pass the global property /p:Test=false in the packing leg for PRs

Note that the Test property has a special meaning in Arcade's build wrapper project which could lead to unexpected behavior: https://github.com/dotnet/arcade/blob/777bc46bd883555cf89b8a68e3e2023fd4f1ee50/src/Microsoft.DotNet.Arcade.Sdk/tools/Build.proj#L106 It controls whether test projects should be run.

You might want to condition on BuildTests instead and pass that in.

[carlossanlop]

Note that the Test property has a special meaning in Arcade's build wrapper project which could lead to unexpected behavior

Classic arcade ☹️.

You might want to condition on BuildTests instead and pass that in.

Between your first suggestion, SkipTests, and BuildTests, I think I prefer SkipTests because the default can be '' or false, and we only need to check the condition if the value is true.