Prune dev dependencies step also runs prepare script

[spatial-andrewc]

Describe the bug

I'm using the buildpack to install dependencies. My application has a prepare script which generates css classes and graphql codegen using the nx tool. The nx tool is a dev dependency. When building the app in Heroku the following steps take place:

1. pnpm install
2. prepare script runs
3. prod build script runs
4. dev dependencies are pruned
5. prepare script runs again

The build fails when step 5 attempts to run the prepare script as it requires dev dependencies.

To Reproduce Steps to reproduce the behavior:

1. Deploy a next js app to heroku that has a dev dependency that is used in the prepare script
2. Create a manual deploy in Heroku
3. Notice that the prepare script attempts to run during the Pruning devDependencies step

Versions (please complete the following information):

• Heroku Stack: heroku-22
• Node Version: 20.4.0
• NPM Version: npm 8.x
• PNPM Version: 8.6.9
• Buildpack Version: latest

Additional context

Log file for the Pruning devDependencies step in Heroku build

-----> Pruning devDependencies

       devDependencies:
       - ... 
       - nx 16.5.0
       - ...

       > my-app@0.0.0 prepare /tmp/build_6499ea3f
       > nx generate-css && nx generate-gql

       sh: 1: nx: not found
        ELIFECYCLE  Command failed.
-----> Build failed

[spatial-andrewc]

Closing as this is a known issue for npm and pnpm.