Reform build process on travis ci

* Change to create "mruby" directory in a repository
* Create Rakefile and use it in .travis.yml
  This enable us to write build script with Ruby syntax

.gitignore

@@ -0,0 +1 @@
+/mruby/

.travis.yml

@@ -6,10 +6,5 @@ before_install:
     - sudo apt-get -qq update
 install:
     - sudo apt-get -qq install rake bison git gperf
-before_script:
-  - cd ../
-  - git clone https://github.com/mruby/mruby.git
-  - cd mruby
-  - cp -fp ../mruby-set/.travis_build_config.rb build_config.rb
 script: 
-  - make all test
+  - rake test

Rakefile

@@ -0,0 +1,22 @@
+MRUBY_CONFIG = File.expand_path(ENV["MRUBY_CONFIG"] || "build_config.rb")
+
+file :mruby do
+  sh "git clone --depth=1 git://github.com/mruby/mruby.git"
+end
+
+desc "compile binary"
+task :compile => :mruby do
+  sh "cd mruby && MRUBY_CONFIG=#{MRUBY_CONFIG} rake all"
+end
+
+desc "test"
+task :test => :mruby do
+  sh "cd mruby && MRUBY_CONFIG=#{MRUBY_CONFIG} rake all test"
+end
+
+desc "cleanup"
+task :clean do
+  sh "cd mruby && rake deep_clean"
+end
+
+task :default => :test

build_config.rb

@@ -2,4 +2,5 @@ MRuby::Build.new do |conf|
   toolchain :gcc
   conf.gembox 'default'
   conf.gem '../mruby-set'
+  conf.enable_test
 end