Describe the bug

Ordinarily, building a Vite app results in import.meta.env.DEV === false and import.meta.env.PROD === true regardless of the mode configuration.

If you set mode when calling vite.build(...) programmatically, however, DEV and PROD are true and false unless the mode happens to be production.

Reproduction

https://github.com/Rich-Harris/vite-mode-repro

System Info

System:
    OS: macOS 12.0.1
    CPU: (10) arm64 Apple M1 Max
    Memory: 779.03 MB / 32.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.15.1 - ~/.nvm/versions/node/v16.15.1/bin/node
    Yarn: 1.22.19 - ~/.nvm/versions/node/v16.15.1/bin/yarn
    npm: 8.11.0 - ~/.nvm/versions/node/v16.15.1/bin/npm
  Browsers:
    Chrome: 103.0.5060.114
    Chrome Canary: 105.0.5187.0
    Firefox: 102.0.1
    Safari: 15.1
  npmPackages:
    vite: ^3.0.2 => 3.0.2

Used Package Manager

npm

Logs

No response

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it's a Vue SFC related bug, it should likely be reported to vuejs/core instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.