New proposal on howto library dependencies could be handled.

Just install ghc68_wrapper which will install the required dependencies ghc
(and libraries) itself.
The list libraries given in the wrapper attribute set can be user tuned in the future ?
An alternative would be creating something similar to the gcc/g++ include/ lib/ scheme which
is could be used by ghc to find installed packages..

svn path=/nixpkgs/trunk/; revision=9581

pkgs/development/compilers/ghc/createGhcWrapper/default.nix

@@ -0,0 +1,25 @@
+args: with args;
+
+stdenv.mkDerivation {
+  inherit suffix name ghc ;
+
+  buildInputs = libraries ++ [ghcPkgUtil];
+
+  phases="installPhase";
+
+  installPhase="
+    ensureDir \$out/bin
+    if test -n \"\$ghcPackagedLibs\"; then
+       g=:\$(echo \$ghc/lib/ghc-*/package.conf)
+    fi
+
+    for a in ghc ghci ghc-pkg; do
+      app=$(ls -al $ghc/bin/$a | sed -n 's%.*-> \\(.*\\)%\\1%p');
+cat > \"\$out/bin/\$a$suffix\" << EOF
+#!`type -f sh | gawk '{ print $3; }'`
+GHC_PACKAGE_PATH=\${GHC_PACKAGE_PATH}\${g} \$ghc/bin/$app \"\\\$@\"
+EOF
+      chmod +x \"\$out/bin/\$a$suffix\"
+    done
+";
+}