llvmPackages: Organize files

Always do pkg/default.nix not pkg.nix; use directories to avoid
prefixing patches and other files.

pkgs/development/compilers/llvm/8/lld/default.nix

@@ -0,0 +1,31 @@
+{ lib, stdenv
+, fetch
+, cmake
+, libxml2
+, llvm
+, version
+}:
+
+stdenv.mkDerivation {
+  pname = "lld";
+  inherit version;
+
+  src = fetch "lld" "121xhxrlvwy3k5nf6p1wv31whxlb635ssfkci8z93mwv4ja1xflz";
+
+  nativeBuildInputs = [ cmake ];
+  buildInputs = [ llvm libxml2 ];
+
+  outputs = [ "out" "dev" ];
+
+  postInstall = ''
+    moveToOutput include "$dev"
+    moveToOutput lib "$dev"
+  '';
+
+  meta = {
+    description = "The LLVM Linker";
+    homepage    = "https://lld.llvm.org/";
+    license     = lib.licenses.ncsa;
+    platforms   = lib.platforms.all;
+  };
+}