Setting --no-frozen-lockfile using nixpacks.

Question

Basically, what I'm trying to achieve is to add the `--no-frozen-lockfile` flag to `pnpm i`.
```toml
[phases.setup]
nixPkgs = ['nodejs', 'pnpm']

[phases.install]
cmd = 'pnpm install --no-frozen-lockfile'

[phases.build]
cmd = 'pnpm run build'
dependsOn = ['install']

[start]
cmd = 'pnpm start' 
```

Issue is - railway still tries to run `pnpm i --frozen-lockfile`.