when outfile format cjs,import the same css file will import a no exists js file

[Veiintc]

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Describe the bug

when outfile format cjs,import the same css file will require a no exists js file

Reproduction

(https://github.com/Veiintc/test-css-codesplit)
npm run build

System Info

• vite version:2.1.1
• Operating System:Window 10
• Node version:14.6.0
• Package manager (npm/yarn/pnpm) and version:6.14.6

Logs (Optional if provided reproduction)

1. Run vite or vite build with the --debug flag.
2. Provide the error log here.