Show the dune error instead of Fatal error: exception Invalid_argument("String.sub / Bytes.sub")

**esy version: 0.5.8**
**Operating System: Archlinux**

**Issue:**

When you have a unclosed parenthesis in your dune file, running `esy` reports:
`Fatal error: exception Invalid_argument("String.sub / Bytes.sub")` while running `esy build -p project` shows:
```
File "lib/dune", line 9, characters 0-0:
Error: unclosed parenthesis at end of input
```

Which is way more helpful.

Reproduce the failure with the reported esy 0.5.8 setup and an unclosed parenthesis in lib/dune. Compare `esy` with `esy build -p project`, then trace the command entry point that turns the dune diagnostic into `Invalid_argument`. Done means esy reports the useful unclosed-parenthesis error instead of the fatal exception.

Written by the indexing model from the issue text.