Add Rakefile to build Groonga

Rakefile

@@ -0,0 +1,23 @@
+require "pathname"
+
+task :default => :build
+
+groonga_version = "4.0.1"
+
+task :build do
+  base_name = "groonga-#{groonga_version}"
+  archive_name = "#{base_name}.tar.gz"
+  sh("curl", "-O", "http://packages.groonga.org/source/groonga/#{archive_name}")
+  sh("tar", "xf", archive_name)
+
+  install_dir = File.join(Dir.pwd, "vendor", "groonga")
+  Dir.chdir(base_name) do
+    sh("./configure",
+       "--prefix=#{install_dir}",
+       "--disable-document")
+    sh("make", "-j")
+    sh("make", "install")
+  end
+
+  sh("tar", "cJf", "heroku-#{base_name}.tar.xz", "vendor/groonga")
+end