Current Behavior:

The following preinstall script:

    {"preinstall": "bash -c 'echo NODE_ENV $NODE_ENV'"}

only prints:
NODE_ENV
when I run npm i --prod

Expected Behavior:

I expect it to print
NODE_ENV production

Steps To Reproduce:

1. configure the above preinstall step in a package.json
2. using npm@6, run npm i --prod
3. using npm@7, run npm i --prod
4. compare results

Environment:

• OS: Ubuntu 20.04
• Node: 12.16.2, npm: 6.14.8
• Node 15.0.0, npm 7.0.3