internal call `opam install --yes PACKAGES` fail in `satyrographos build`

[yasuo-ozu]

It occurs when Satyristes has no dependencies, like:

(lang 0.0.3)
(doc
  (name "aaa")
  (workingDirectory "./")
  (build (
    (make-with-env-var "aaa.pdf")
  ))
  (dependencies ())
)

The cause is the following line.
https://github.com/na4zagin3/satyrographos/blob/master/src/command/build.ml#L138
The code does not consider when dependencies has no item.