One of ghc's dependencies for armv7h is llvm.
The llvm package is version 3.6, which is not compatible with ghc.
I tried installing llvm35 doing pacman -Sdd llvm35 llvm35-libs.
ghc seems to be able to compile now, it does still complain however that this version of llvm hasn't been tested.
I do know that the latest version of ghc works perfectly with llvm35.
But I haven't noticed any problems with this one yet.
Should the dependencies of the ghc package be changed?