new-haddock: '-dynamic' flag is not passed to haddock (archlinux, dynamic GHC package)

[TimoFreiberg]

~/.cabal/config:

library-vanilla: False
shared: True
executable-dynamic: True

GHC version: 8.2.1
Cabal version: 2.1.0

ghc and setup are called with -dynamic, but haddock isn't.
The operation fails with a linker error.
Passing -optghc=-dynamic to haddock (via --haddock-options) fixed the issue.

I since went static again after I found ghc-static and don't use the dynamic settings anymore.

[alexbiehl]

The culprit is most likely here: https://github.com/haskell/cabal/blob/master/Cabal/Distribution/Simple/Haddock.hs#L329

    opts <- if withVanillaLib lbi
            then return vanillaOpts
            else if withSharedLib lbi
            then return sharedOpts
            else die' verbosity $ "Must have vanilla or shared libraries "
                       ++ "enabled in order to run haddock"

Where sharedOpts includes -dynamic.

Indeed if one passes --disable-library-vanilla Cabal picks sharedOpts. So I think we need the same mechanism here with which cabal-install decides if it should pass -dynamic to ghc and setup or not.