gcc45, gnat, ghdl: fix up the builds

Some parts are slightly puzzling, but it seems to work and it didn't
seem economical to put more effort into it.

pkgs/development/compilers/ghdl/default.nix

@@ -1,9 +1,4 @@
 { stdenv, fetchurl, gnat, zlib }:
-
-# I think that mcode can only generate x86 code,
-# so it fails to link pieces on x86_64.
-assert stdenv.system == "i686-linux";
-
 let
   version = "0.33";
 in
@@ -22,13 +17,17 @@ stdenv.mkDerivation rec {
     sed -i s/-gnatwae/-gnatwa/ Makefile.in ghdl.gpr.in
   '';
 
+  hardeningDisable = [ "all" ];
+
   enableParallelBuilding = true;
 
   meta = {
     homepage = "http://sourceforge.net/p/ghdl-updates/wiki/Home/";
     description = "Free VHDL simulator, mcode flavour";
     maintainers = with stdenv.lib.maintainers; [viric];
-    platforms = with stdenv.lib.platforms; linux;
+    # I think that mcode can only generate x86 code,
+    # so it fails to link pieces on x86_64.
+    platforms = with stdenv.lib.platforms; [ "i686-linux" ];
     license = stdenv.lib.licenses.gpl2Plus;
   };
 }