ffmpegthumbnailer: fix Mountain Lion build.

This also uses the args the INSTALL file says to use, adds the head url,
and uses the release tarball instead of the source tarball.

Closes Homebrew/homebrew#49293.
Closes Homebrew/homebrew#49296.

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

Formula/ffmpegthumbnailer.rb

@@ -1,8 +1,9 @@
 class Ffmpegthumbnailer < Formula
   desc "Create thumbnails for your video files"
   homepage "https://github.com/dirkvdb/ffmpegthumbnailer"
-  url "https://github.com/dirkvdb/ffmpegthumbnailer/archive/2.1.1.tar.gz"
-  sha256 "e43d8aae7e80771dc700b3d960a0717d5d28156684a8ddc485572cbcbc4365e9"
+  url "https://github.com/dirkvdb/ffmpegthumbnailer/releases/download/2.1.1/ffmpegthumbnailer-2.1.1.tar.bz2"
+  sha256 "f1f1b54b7903d726a118d7b2a2992cacef561517567f3a547964ad48cb5c89bd"
+  head "https://github.com/dirkvdb/ffmpegthumbnailer.git"
 
   bottle do
     cellar :any
@@ -18,7 +19,13 @@ class Ffmpegthumbnailer < Formula
   depends_on "ffmpeg"
 
   def install
-    system "cmake", *std_cmake_args
+    ENV.cxx11 if MacOS.version < :mavericks
+
+    args = std_cmake_args
+    args << "-DENABLE_GIO=ON"
+    args << "-DENABLE_THUMBNAILER=ON"
+
+    system "cmake", *args
     system "make"
     system "make", "install"
   end