Use cabal sandboxes for building UHC

[phile314]

UHC could be built inside a cabal sandbox instead of using the global package db. This would avoid
any collisions between wrong package versions already installed.

Just an idea, not a problem for me. Would make it easier for other people to install it I think.

[seaneshbaugh]

Seconding this. In general I prefer to use sandboxed libraries if possible. I admittedly didn't try very hard, but I couldn't figure out a way to get make to work with sandboxed libraries. I was able to get configure to work by adding "--package-db" to the call to ghc-pkg in the configure script.

[phile314]

The Nix package for UHC actually does something similar, although it does not use sandboxes but just plain ghc-pkg. But it at least points out where the changes need to be made.

https://github.com/NixOS/nixpkgs/blob/master/pkgs/development/compilers/uhc/default.nix#L23-L36

[wrengr]

I'd also be interested in getting Cabal sandboxes to work for compiling UHC