Update fltk.rb to support HEAD for OS X El Capitan

Library/Formula/fltk.rb

@@ -1,8 +1,6 @@
 class Fltk < Formula
   desc "Cross-platform C++ GUI toolkit"
   homepage "http://www.fltk.org/"
-  url "https://fossies.org/linux/misc/fltk-1.3.3-source.tar.gz"
-  sha256 "f8398d98d7221d40e77bc7b19e761adaf2f1ef8bb0c30eceb7beb4f2273d0d97"
 
   bottle do
     sha1 "33c75cce41deadbfe54bdcc22ae91d17d3ecc782" => :mavericks
@@ -11,27 +9,42 @@ class Fltk < Formula
 
   option :universal
 
+  stable do
+    url "https://fossies.org/linux/misc/fltk-1.3.3-source.tar.gz"
+    sha256 "f8398d98d7221d40e77bc7b19e761adaf2f1ef8bb0c30eceb7beb4f2273d0d97"
+
+    # Fixes issue with -lpng not found.
+    # Based on: https://trac.macports.org/browser/trunk/dports/aqua/fltk/files/patch-src-Makefile.diff
+    patch :DATA
+
+    # Fltk 1.3.4 include support for El Capitan. Remove on update.
+    depends_on MaximumMacOSRequirement => :yosemite
+  end
+
+  head do
+    url "http://seriss.com/public/fltk/fltk/branches/branch-1.3/", :using => :svn
+    depends_on "cmake" => :build
+  end
+
   depends_on "libpng"
   depends_on "jpeg"
 
-  # Fltk 1.3.4 include support for El Capitan. Remove on update.
-  depends_on MaximumMacOSRequirement => :yosemite
-
   fails_with :clang do
     build 318
     cause "http://llvm.org/bugs/show_bug.cgi?id=10338"
   end
 
-  # Fixes issue with -lpng not found.
-  # Based on: https://trac.macports.org/browser/trunk/dports/aqua/fltk/files/patch-src-Makefile.diff
-  patch :DATA
-
   def install
     ENV.universal_binary if build.universal?
-    system "./configure", "--prefix=#{prefix}",
-                          "--enable-threads",
-                          "--enable-shared"
-    system "make", "install"
+    if build.head?
+        system "cmake", ".", *std_cmake_args
+        system "make", "install"
+    else
+        system "./configure", "--prefix=#{prefix}",
+                              "--enable-threads",
+                              "--enable-shared"
+        system "make", "install"
+    end
   end
 end