Build order:

I started from EPEL5 ghc-7.0.4 and ghc-rpm-macros.
An easy way to fetch the tarballs is to use cabal-rpm or fedpkg.

# GHC
1a on RHEL6 only: gcc44 (dummy compat package)
1b bootstrap/ghc
1c bootstrap/hscolour
1d ghc-rpm-macros
1e ghc

# Haskell Platform
2a ghc-primitive
2b ghc-split
2c ghc-vector
2d haskell-platform

(or cabal-install)

# Cabal-dev
6a ghc-tar
6b cabal-dev

# Hsb2hs
7. hsb2hs