How do I quote a variable to use in `arguments` in a package? If I'm reading the scheme right, `arguments` is a thunked field, so it gets evaluated in a different context. How do I take something from the defining context?

```
(define phases ...)

(define-public cool-package-name
  (guix-packages:package
    ; ...
    (arguments `(
       #:phases ,phases)))
```

Without the unquote in front of phases, guile build says "phases is undefined." With the unquote it says "Unknown # object: #\<".