Add upper bound on ghcjs-base back into -jsffi

[hamishmack]

PR #105 relaxed the ghcjs-base bound on ghcjs-dom-jsffi, but the fix was for ghcjs-dom-javascript. We should not be using both ghcjs-dom-jsffi and ghcjs-dom-javascript at the same time.

Packages should either depend on ghcjs-dom only (and let it choose the correct implementation library) or do something like:

if impl(ghc >9)
  build-depends: ghcjs-dom-javascript
else
  build-depends: ghcjs-dom-jsffi

[hamishmack]

@sevanspowell can you please check adding this bound back will work for servant-jsaddle. I think something might be depending on ghcjs-dom-jsffi when it should not.

[sevanspowell]

Of course. I was getting this error:

[__0] trying: ghcjs-base-0.8.0.0 (user goal)
[__1] next goal: ghcjs-dom-jsffi (user goal)
[__1] rejecting: ghcjs-dom-jsffi-0.9.9.0 (conflict: ghcjs-base==0.8.0.0,
ghcjs-dom-jsffi => ghcjs-base>=0.2.0.0 && <0.3)

After a bit of investigation, it's because I had added a cabal.project file to servant-jsaddle (my fork at least), that referenced the "ghcjs-dom-jsffi" subdir:

source-repository-package
    type: git
    location: https://github.com/ghcjs/ghcjs-dom.git
    tag: 7cdeedd873f76969f3144b7052c6f594d8b37bf8
    --sha256: 130cz1i77mjvicczn5yhci4b14z9gxk5xxi1b4ych5x0k3qvnnjb
    subdir:
      ghcjs-dom
      ghcjs-dom-jsaddle
      ghcjs-dom-javascript
      ghcjs-dom-jsffi

So having that subdir there added a constraint on the package, which I didn't expect. It was enough to remove them:

source-repository-package
    type: git
    location: https://github.com/ghcjs/ghcjs-dom.git
    tag: 7cdeedd873f76969f3144b7052c6f594d8b37bf8
    --sha256: 130cz1i77mjvicczn5yhci4b14z9gxk5xxi1b4ych5x0k3qvnnjb
    subdir:
      ghcjs-dom

Sorry about that. Good to go now. Thanks for clarifying that ghc > 9 ? ghcjs-dom-javascript : ghcjs-dom-jsffi, good to know.