Could someone confirm for me whether OS/X Lion is supported for
Haskell platform (or more likely) there's a different way of going
about installation?
The problem is not Lion, it is that
(a) Xcode 4.3 was only just released
(b) Apple does not allow details of unreleased software to be discussed etc. before release
which means
(c) everyone who relies on Xcode got pretty much blindsided by all the changes.
ghc hasn't quite caught up with the changes yet. MacPorts is still struggling with some issues involved with the release; I don't know where Homebrew is with respect to it. Some of the other projects I'm involved with aren't Mac focused, and are just starting to realize that there are problems with Xcode 4.3 support.
If you need Haskell Platform working ASAP on OS X, remove Xcode 4.3, then download Xcode 4.2.1 from
http://connect.apple.com/.