haskell-file-embed, haskell-hamlet, and haskell-clientsession were all modified to build-depend on ghc-ghci, "to avoid build attempts on arches without template haskell". Those packages fail on powerpc and sparc because nothing on those arches provide ghc-ghci. The ghc package on both powerpc and sparc contain the ghci binary and template-haskell library. I have no idea what any of these things have to do with each other.