[web, wasm] if build omits --wasm do a "dry run" wasm build to give users their wasm-ability #163163
Description
Need to discuss UX here.
If it fails, we need to talk about making the output prettier (right now it's hard to see the failures)
If it succeeds, we should "encourage" the user to turn things on.
Also need to discuss analytics here – so we can track the % of builds that "would" fail.