remove dead make-symlinks builder

Introduced in 5808ac7148, never used again
after b06335a835.

pkgs/build-support/make-symlinks/builder.sh

@@ -1,9 +0,0 @@
-source $stdenv/setup
-
-mkdir $out
-for file in $files
-do
-  subdir=`dirname $file`
-  mkdir -p $out/$subdir
-  ln -s $dir/$file $out/$file
-done

pkgs/build-support/make-symlinks/default.nix

@@ -1,7 +0,0 @@
-{name ? "", stdenv, dir, files}:
-
-stdenv.mkDerivation {
-  inherit dir files;
-  name = if name == "" then dir.name else name;
-  builder = ./builder.sh;
-}