ILLink is no longer crossgen'd

[sbomer]

With the change to download a linker package that matches the target framework (dotnet/sdk#29441), ILLink is no longer bundled with the SDK and therefore is no longer going to be crossgen'd (see dotnet/installer#15151 (comment)).

Opening this as a tracking issue in case we want to do something about that. Let's keep an eye on the build performance. If we need to, we could probably ship RID-specific ILLink packages that are crossgen'd as part of the runtime build.

[LXGaming]

Documenting an issue I encountered with GitHub Actions Runner ubuntu22/20231115.7 (includes .NET 8) when building a .NET 7 project.

I use GitHub Actions for publishing trimmed .NET binaries, my workflow consists of a restore step and all subsequent steps use --no-restore, I found that builds were no longer being trimmed due to ILLink having disappeared. I eventually stumbled upon this issue and its linked PRs which noted that a restore would be required for ILLink to be downloaded, because I use /p:PublishTrimmed=true and --no-restore on the publish command ILLink is never downloaded.

The solution is to add /p:PublishTrimmed=true to the restore command or alternatively avoid using --no-restore to ensure that ILLink is present.

I believe there should be a warning or error when PublishTrimmed is specified but ILLink isn't present.

[sbomer]

Thanks for reporting @LXGaming, let's track that in dotnet/sdk#37049.