Very basic cli to compile ruby files

Off course this is basically a cross compiler and the files
have to be transferred to an arm machine (and fixed as per note)
close #22

bin/rubyxc

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+#! /usr/bin/env ruby -I lib
+require 'rubygems'
+require 'bundler'
+begin
+  Bundler.setup(:default)
+rescue Bundler::BundlerError => e
+  $stderr.puts e.message
+  $stderr.puts "Run `bundle install` to install missing gems"
+  exit e.status_code
+end
+
+require "rubyx/rubyxc"
+
+RubyXC.start(ARGV)

lib/rubyx/rubyxc.rb

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+require "thor"
+require "rubyx"
+
+class RubyXC < Thor
+  desc "compile FILE" , "Compile given FILE to binary"
+  long_desc <<-LONGDESC
+      Very basic cli to compile ruby programs.
+      Currently only compile command supported without option.
+
+      Output will be elf object file of the same name, with .o, in root directory.
+
+      Note: Because of Bug #13, you need to run "ld -N file.o" on the file, before
+      executing it. This can be done on a mac by installing a cross linker
+      (brew install arm-linux-gnueabihf-binutils), or on the target arm machine.
+    LONGDESC
+
+  def compile(file)
+    begin
+      ruby = File.read(file)
+    rescue
+      fail MalformattedArgumentError , "No such file #{file}"
+    end
+    puts "compiling #{file}"
+
+    linker = ::RubyX::RubyXCompiler.new.ruby_to_binary( ruby , :arm )
+    writer = Elf::ObjectWriter.new(linker)
+
+    outfile = file.split("/").last.gsub(".rb" , ".o")
+    writer.save outfile
+
+    return outfile
+  end
+end

test/rubyx/test_rubyxc.rb

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+require_relative "helper"
+require "rubyx/rubyxc"
+
+module RubyX
+  class TestRubyXCli < MiniTest::Test
+
+    def test_invoke_without_not_work
+      assert_output(nil , /not find/) {RubyXC.start(["list"])}
+    end
+    def test_invoke_compile_works
+      assert_output( "") {RubyXC.start(["compile" ])}
+    end
+    def test_file_fail
+      assert_output(nil , /No such file/) {RubyXC.start(["compile" , "hi"])}
+    end
+    def test_file_open
+      assert_output(/compiling/) {RubyXC.start(["compile" , "test/mains/source/add__4.rb"])}
+      File.delete "add__4.o"
+    end
+  end
+end