feat: log a warning if dependency pre-bundling cannot be run

[benmccann]

Description

Log a warning if dependency pre-bundling cannot be run

Additional context

It turns out that SvelteKit was entirely skipping dependency pre-bundling. I think this has been part of the reason that we've gotten so many reports from people not being able to use CJS dependencies. There's still multiple other issues preventing CJS from working in Vite, but we've at least fixed the SvelteKit portion of it now. It would have been very nice to realize this earlier, but took a fair amount of debugging to figure out. Hopefully this will save other people from hitting the same issue

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What is the purpose of this pull request?

• Bug fix
• New Feature
• Documentation update
• Other

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[yyx990803]

This warning is technically wrong because it logs even when

1. the user explicitly sets the entry to an empty array
2. When there is no resolved entrypoints, but the user has explicit optimizeDeps.include.

Fixed in b586098