>>9GHC is written in Haskell, the runtime system is in C.
Also, the reason shitty buggy languages are used to implement better languages is that the OS infrastructure which is unfortunately written in them already.
Still, there are wrappers and bindings so that the C or Sepples exposure may be minimal. E.g.
http://www.stephendiehl.com/llvm/Anyway, languages like Idris or Agda are implemented in Haskell, so your star argument is actually pretty stale.