tup: fix compilation of HEAD version in Yosemite

Do not try to apply an outdated patch. Backport upstream commit instead
of abandoned PR.

Closes Homebrew/homebrew#38288.

Signed-off-by: Mike McQuaid <mike@mikemcquaid.com>

Formula/tup.rb

@@ -16,12 +16,13 @@ class Tup < Formula
   depends_on "pkg-config" => :build
   depends_on :osxfuse
 
-  # Fixes the renaming of functions on OS X 10.10
-  # https://github.com/gittup/tup/issues/204
-  if MacOS.version >= :yosemite
-    patch do
-      url "https://github.com/gittup/tup/pull/205.diff"
-      sha1 "eebe8293b18096361130d0a97e0f10c524a716b3"
+  # Backport Yosemite compilation fix
+  stable do
+    if MacOS.version >= :yosemite
+      patch do
+        url "https://github.com/gittup/tup/commit/9812548b4d3833644f0cf8f70f62628a75ffbb56.diff"
+        sha1 "439fb1e1692c95e09703d6c41055c06855276307"
+      end
     end
   end