The resident compiler mode should not emit content on stdout

[jakemac53]

When running dart run -r <script>, if the resident compiler is not already active then it will emit some text on stdout telling you it has started it.

This breaks any apps which are communicating over stdin/stdout, especially using JSON-RPC2. Specifically, this breaks the dart MCP server.

These messages should only be emitted on stderr or not at all (I don't think they serve any purpose anyways, there is no action for a developer to take).

[jakemac53]

cc @bkonyi I don't know what area to assign this to, maybe you do? Not sure where the resident compiler stuff is handled.

[lrhn]

If it's dart-cli-run, it's probably area-dart-cli.

If nothing else, the Dart CLI should have some flag to silence diagnostics.

[jakemac53]

If nothing else, the Dart CLI should have some flag to silence diagnostics.

Fwiw I really don't think this output is useful to anybody at all, there is no action to take based on it. A flag will be hard for people to discover and they will just end up filing bugs like this one.

If we go the flag approach, we should default it to off.