Verify canary release

• I verified that the issue exists in the latest Next.js canary release

Provide environment information

Operating System:
  Platform: darwin
  Arch: arm64
  Version: Darwin Kernel Version 23.6.0: Fri Jul  5 17:56:41 PDT 2024; root:xnu-10063.141.1~2/RELEASE_ARM64_T6000
  Available memory (MB): 32768
  Available CPU cores: 8
Binaries:
  Node: 20.12.0
  npm: 10.5.0
  Yarn: 1.22.19
  pnpm: 9.7.0
Relevant Packages:
  next: 14.2.6 // Latest available version is detected (14.2.6).
  eslint-config-next: 14.2.6
  react: 18.3.1
  react-dom: 18.3.1
  typescript: 5.5.4
Next.js Config:
  output: standalone

Which example does this report relate to?

none

What browser are you using? (if relevant)

No response

How are you deploying your application? (if relevant)

No response

Describe the Bug

cannot set env variables in run time, all env, not only the one that start with NEXT_PUBLIC_ are embedded in process.env in build time and cannot be changed.

Expected Behavior

be able to pass server env variables in run time.

To Reproduce

https://github.com/galgue/nextjs-runtime-env/tree/main
run npm run build
go to .next/standalone folder and run RUN_TIME=1 node server.js
in the browser browse into http://localhost:3000/api/health to get the env variable.

expect to see RUN_TIME=1 but we get undefined.