haskell lib: Make Cabal compiler names explicit

Cabal2nix expects a --compiler flag that contains a Cabal Compiler description.
We used to use the compiler's derivation name for this, but this breaks when
cross-compiling due to the target suffix. Instead we add an explicit
haskellCompilerName attribute to Haskell compiler derivations.

pkgs/development/haskell-modules/make-package-set.nix

@@ -120,7 +120,7 @@ let
       installPhase = ''
         export HOME="$TMP"
         mkdir -p "$out"
-        cabal2nix --compiler=${self.ghc.name} --system=${stdenv.system} ${sha256Arg} "${src}" > "$out/default.nix"
+        cabal2nix --compiler=${ghc.haskellCompilerName} --system=${stdenv.system} ${sha256Arg} "${src}" > "$out/default.nix"
       '';
   };