Wow this one was tricky to catch! So here's the issue: basically Railway lets you add whitespace around the names of env vars, and it won't trim() that automatically. Now, this might be fine (though, I've never heard of an env var with whitespace) but with how Nixpacks handles formatting ENV vars, it breaks things.

In particular, this line: https://github.com/railwayapp/nixpacks/blob/87aeabb09d61b693389a2e8d0d4b560014ce259a/src/nixpacks/builder/docker/dockerfile_generation.rs#L143-L161

That said, the above code looks and runs fine with normal env vars.

The issue is that because there's no trim() around the whitespace, the env vars will also have a space between them. What this leads to is instead of this: ENV=$ENV you get this: ENV =$ENV. This then results in all env vars having an = appending to them.

This is confirmed in the build logs:
```
LegacyKeyValueFormat: "ENV key=value" should be used instead of legacy "ENV key value" format (line 18)
```

I can't really think of a reason we wouldn't .trim() env vars, so that'd be my vote. But if we can't do that, then we need to update the above code in nixpacks to handle that somehow.