Disable Yarn warnings on CI builds for restore and Blazor WebAssembly projects

[javiercn]

Fixes #22251 and #22240.

The approach is to disable the warnings when we run the command on the CI and leave them on Dev builds.

I tried to use CustomWarningRegularExpression but that is not available on ToolTask (only exec task) so this is the best we can do.

[dougbu]

This works but I think we should take a close look at the Yarn.MSBuild SDK. According to @mmitche it's part of the reason our builds are as slow as they are and a lot of the reason our binary logs are useless. The inability to suppress the specific warning we're seeing is another strike against it; I worry about missing other issues in the future.

[javiercn]

This works but I think we should take a close look at the Yarn.MSBuild SDK. According to @mmitche it's part of the reason our builds are as slow as they are and a lot of the reason our binary logs are useless. The inability to suppress the specific warning we're seeing is another strike against it; I worry about missing other issues in the future.

That's fine, can you file a separate issue for that and we can add that to the DoI agenda? Since it affects SignalR, Templates and Components among other things.

For what we are trying to accomplish here, this change should be enough in the mean time.

[dougbu]

this change should be enough in the mean time.

Agreed

[dougbu]

Filed #22723