Describe the bug

process.env.NODE_ENV gets replaced and removes code in library mode. This is an undesirable behaviour as i want to have this check in the project i'm going to import the library.

Reproduction

export const testFunction = () => {
  if (process.env.NODE_ENV === 'development') {
    alert('This is a Test');
  }
}

if build with vite build using this config:

import { defineConfig } from 'vite';
import * as path from 'path';

export default defineConfig({
  build: {
    lib: {
      entry: path.resolve(__dirname, 'src/index.ts'),
      name: 'myProject',
    },
  },
});

it will become:

const testFunction = () => {
};

System Info

Output of npx envinfo --system --npmPackages vite,@vitejs/plugin-vue --binaries --browsers:

  System:
    OS: Windows 10 10.0.19041
    CPU: (4) x64 Intel(R) Core(TM) i5-7600K CPU @ 3.80GHz
    Memory: 8.36 GB / 15.94 GB
  Binaries:
    Node: 12.16.3 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.5 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 6.14.5 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Chrome: 90.0.4430.93
    Edge: Spartan (44.19041.906.0), Chromium (90.0.818.51)
    Internet Explorer: 11.0.19041.1
  npmPackages:
    vite: ^2.2.3 => 2.2.3

Used package manager: npm

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