ghc version bump to latest stable release 6.12.1

make cabal expression add etxra library paths only if they exist.
Adding myself as maintainer so that the buildfarm builds ghc.

svn path=/nixpkgs/trunk/; revision=19198

pkgs/development/compilers/ghc/6.12.1.nix

@@ -1,15 +1,15 @@
 {stdenv, fetchurl, ghc, perl, gmp, ncurses}:
 
 stdenv.mkDerivation rec {
-  version = "6.12.0.20091010";
+  version = "6.12.1";
   
   name = "ghc-${version}";
   
   homepage = "http://haskell.org/ghc";
 
   src = fetchurl {
-    url = "http://darcs.haskell.org/~ghc/dist/6.12.1rc1/${name}-src.tar.bz2";
-    sha256 = "903552917778329fc79cc273ece81030324006f47157ddd4278cb08c1c637fd3";
+    url = http://haskell.org/ghc/dist/6.12.1/ghc-6.12.1-src.tar.bz2;
+    sha256 = "0ajm4sypk4zgjp0m6i03fadyv5dm9vlqfnvsx1g94yk7vnd9zyfd";
   };
 
   buildInputs = [ghc perl gmp ncurses];
@@ -34,6 +34,8 @@ stdenv.mkDerivation rec {
   meta = {
     inherit homepage;
     description = "The Glasgow Haskell Compiler";
+    maintainers = [stdenv.lib.maintainers.marcweber];
+    platforms = stdenv.platforms.linux;
   };