gccgo46: removing it. I set gccgo = gcc47

gccgo46 did not build for me, and maybe never built at all.
The same recipe, though, worked fine for gcc47. So let's go with gcc47.

pkgs/development/compilers/gcc/4.7/default.nix

@@ -43,6 +43,9 @@ assert libelf != null -> zlib != null;
 # Make sure we get GNU sed.
 assert stdenv.isDarwin -> gnused != null;
 
+# The go frontend is written in c++
+assert langGo -> langCC;
+
 with stdenv.lib;
 with builtins;
 

pkgs/top-level/all-packages.nix

@@ -2206,18 +2206,12 @@ let
     inherit fetchurl stdenv;
   });
 
-  gccgo = gccgo46;
+  # gccgo46 does not work. I set 4.7 then.
-
+  gccgo = gccgo47;
-  gccgo46 = wrapGCC (gcc46_real.gcc.override {
-    name = "gccgo";
-    langCC = true; #required for go
-    langC = true;
-    langGo = true;
-  });
 
   gccgo47 = wrapGCC (gcc47_real.gcc.override {
     name = "gccgo";
-    langCC = true; #required for go
+    langCC = true; #required for go.
     langC = true;
     langGo = true;
   });