Skip signing VisualFsharp.sln and FSharp.sln when building with .NET …

[ellahathaway]

Closes#18112

May need to be adjusted based on #18112 (comment)

When VisualFSharp.sln and FSharp.sln are built with .NET Core MSBuild, no artifacts are built that can be signed -> signing fails when an empty ItemsToSign list.

This PR includes a change that sets -sign to false when building VisualFSharp.sln or FSharp.sln with .NET Core on windows.

[github-actions]

✅ No release notes required

[ellahathaway]

Marking this as ready for review. This change is needed to unblock dotnet/sdk#44855. Depending on the feedback to #18112 (comment), I'm happy to either revise this PR or open a follow up PR later.

[ellahathaway]

@dotnet/fsharp-team-msft - friendly ping. Can I please get eyes on this? It's needed to enable signing in the VMR for the unified build project.

put it my mistake

[psfinaki]

@ellahathaway sorry for the delay. We are waiting for @KevinRansom to take a look at this as he's most knowledgeable in the topic.

If this is in a hurry && low risk, we can probably merge it as is and hope things work out. Letting @T-Gro to decide tho.

[KevinRansom]

@ellahathaway sorry for the delay I was in England. But now Jet-lag has my attention.