Environment variables don't seem to get used by anvil builds

[rehno-lindeque]

When upgrading/adding a lot of dependencies in your .cabal file it will often fail to install unless you add --force-reinstall.

Should we add a flag to run this?

cabal sandbox delete; cabal sandbox init; cabal sandbox install --only-dependencies

It feels a little bit awkward to do all of these sorts of operations via environment variables - would be nice if this was more automatic. I'm not really sure what the best practice is for upgrading cabal dependencies these days, I usually just delete the sandbox and start over when I run into problems...

(Although, perhaps I'm missing something, is this what cabal-constraints is intended for?)

[rehno-lindeque]

Actually I think it might just be that that the CLEAR_BUILDPACK_CACHE: 1 flag doesn't seem to work with anvil (i.e. heroku build -r -b https://github.com/begriffs/heroku-buildpack-ghc.git). I forced rebuilding with a branch heroku build -r -b https://github.com/rehno-lindeque/heroku-buildpack-ghc.git#rebuild and that did the trick...