ghostscript: fix patching file that differs between stable and HEAD

This is fragile but unfortunately it's required.

Fixes Homebrew/homebrew#27550.

Formula/ghostscript.rb

@@ -2,9 +2,14 @@ require 'formula'
 
 class Ghostscript < Formula
   homepage 'http://www.ghostscript.com/'
+
+  stable do
     url 'http://downloads.ghostscript.com/public/ghostscript-9.10.tar.gz'
     sha1 '29d6538ae77565c09f399b06455e94e7bcd83d01'
 
+    patch :DATA # Uncomment OS X-specific make vars
+  end
+
   bottle do
     sha1 "be9d9be82c03ac8409994fee0cc638d20ceb145c" => :mavericks
     sha1 "667bbb27e64fee6d46da07c98205a6daf51a28ad" => :mountain_lion
@@ -21,6 +26,12 @@ class Ghostscript < Formula
     depends_on :autoconf
     depends_on :automake
     depends_on :libtool
+
+    # Uncomment OS X-specific make vars
+    patch do
+      url "https://gist.githubusercontent.com/jacknagel/9559501/raw/9709b3234cc888d29f717838650d29e7062da917/gs.patch"
+      sha1 "65c99df4f0d57368a086154d34722f5c4b9c84cc"
+    end
   end
 
   option 'with-djvu', 'Build drivers for DjVU file format'
@@ -49,11 +60,6 @@ class Ghostscript < Formula
     sha1 'c7d0677dae5fe644cf3d714c04b3c2c343906342'
   end
 
-  # Fix dylib names, per installation instructions
-  def patches
-    DATA
-  end
-
   def move_included_source_copies
     # If the install version of any of these doesn't match
     # the version included in ghostscript, we get errors