treewide: mark bad packages

Some old stuff is known not to work.

pkgs/development/compilers/llvm/3.7/libc++/default.nix

@@ -43,5 +43,6 @@ stdenv.mkDerivation rec {
     description = "A new implementation of the C++ standard library, targeting C++11";
     license = with stdenv.lib.licenses; [ ncsa mit ];
     platforms = stdenv.lib.platforms.unix;
+    badPlatforms = [ "x86_64-darwin" ];
   };
 }

pkgs/development/compilers/llvm/4/lld.nix

@@ -27,5 +27,6 @@ stdenv.mkDerivation {
     homepage    = http://lld.llvm.org/;
     license     = stdenv.lib.licenses.ncsa;
     platforms   = stdenv.lib.platforms.all;
+    badPlatforms = [ "x86_64-darwin" ];
   };
 }

pkgs/development/compilers/llvm/5/lld.nix

@@ -27,5 +27,6 @@ stdenv.mkDerivation {
     homepage    = http://lld.llvm.org/;
     license     = stdenv.lib.licenses.ncsa;
     platforms   = stdenv.lib.platforms.all;
+    badPlatforms = [ "x86_64-darwin" ];
   };
 }