The SDK should issue a build warning when building a macOS app that likely won't run #51432
Description
Is your feature request related to a problem? Please describe.
On macOS, applications ending in .App or .Service just....don't work with dotnet run. The SDK should give users a heads-up so that we can 'shift-left' this user foot-gun.
Describe the solution you'd like
The SDK should add a new diagnostic (level=warning) that is fired when a project with an OutputType of Exe is
- built at all when the SDK's 'implicit RuntimeIdentifier' is a macOS RID, and/or
- whenever such a project is built with a RID that is a macOS RID
Additional context
This bites users somewhat frequently (I've hit it in the past) and is difficult to solve when it does pop up: dotnet/runtime#120935