Ability to pass non-standard command-line options to dart2js #99015

Use case

In order for the the dart2js team to properly support Flutter-web customers, we sometimes need the customer to pass non-standard options to dart2js. Examples include disabling a specific optimization, or dumping some kinds of compiler debug state.

Proposal

• A way to pass arbitrary argument(s) through to dart2js.
• A web page documenting how to use this feature so that it can be referenced in a reply to an issue filed by the customer.