optparse-applicative-0.19 support (to get back in Stackage Nightly)

optparse-applicative-0.19 is now used in Stackage: https://www.stackage.org/nightly-2025-07-15/package/optparse-applicative-0.19.0.0

But this version is not supported by Dhall. It would be nice to support it such that people could get access to Dhall easily by using Stackage.

Fixed in

* #2659