Remove endian configuration methods.

Since we made our opcode byte based, we need no endian option (`-e`
and `-E`) to `mrbc`.

lib/mruby/build.rb

@@ -388,26 +388,5 @@ EOS
         @test_runner.run(mrbtest)
       end
     end
-
-    def big_endian
-      if @endian
-        puts "Endian has already specified as #{@endian}."
-        return
-      end
-      @endian = :big
-      @mrbc.compile_options += ' -E'
-      compilers.each do |c|
-        c.defines += %w(MRB_ENDIAN_BIG)
-      end
-    end
-
-    def little_endian
-      if @endian
-        puts "Endian has already specified as #{@endian}."
-        return
-      end
-      @endian = :little
-      @mrbc.compile_options += ' -e'
-    end
   end # CrossBuild
 end # MRuby