Rollup options for `watch` not respected

[susnux]

Describe the bug

When settings rollup options for the watcher those are ignored / not passed to rollup by vite.
Meaning this does not work:

build: {
  rollupOptions: {
    watch: { allowInputInsideOutputPath: true },
  },
}

See reproduction below.

Alternative I considered is to use the vite option for watch but that will always trigger watching sources - but I want to do it conditionally based on the vite flag (e.g. to have npm run build and npm run watch), see also #20657 .

Reproduction

https://stackblitz.com/edit/vitejs-vite-acyxuft1?file=vite.config.js,package.json,package-lock.json&terminal=dev

Steps to reproduce

Just run npx vite build --watch

System Info

System:
    OS: Linux 5.0 undefined
    CPU: (8) x64 Intel(R) Core(TM) i9-9880H CPU @ 2.30GHz
    Memory: 0 Bytes / 0 Bytes
    Shell: 1.0 - /bin/jsh
  Binaries:
    Node: 20.19.1 - /usr/local/bin/node
    Yarn: 1.22.19 - /usr/local/bin/yarn
    npm: 10.8.2 - /usr/local/bin/npm
    pnpm: 8.15.6 - /usr/local/bin/pnpm
  npmPackages:
    vite: ^7.1.3 => 7.1.3

Used Package Manager

npm

Logs

No response

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