Errors encountered during prerender do not exit the process with failure code

[gryphonmyers]

Reproduction Steps:

1. Execute prerender command for a site that throws an error in a used prerender hook, followed by another command e.g. npm run prerender && echo 'hi'
2. Observe that after the error is thrown and the prerender process fails, the second command is executed.

Expected Results:
Any error encountered during prerender should immediately exit the process via process.exit(1) to prevent operations downstream (e.g. deploying a broken site).