update mrbgem.rake

mrbgem.rake

@@ -1,17 +1,6 @@
 MRuby::Gem::Specification.new('mruby-syslog') do |spec|
   spec.license = 'MIT'
   spec.authors = 'mruby developers'
-
-  # spec.cflags = ''
-
-  # spec.mruby_cflags = ''
-  # spec.mruby_ldflags = ''
-  # spec.mruby_libs = ''
-  spec.mruby_includes = ["#{build.root}/src"]
-
-  # spec.rbfiles = Dir.glob("#{dir}/mrblib/*.rb")
-  # spec.objs = Dir.glob("#{dir}/src/*.{c,cpp,m,asm,S}").map { |f| f.relative_path_from(dir).pathmap("#{build_dir}/%X.o") }
-  # spec.test_rbfiles = Dir.glob("#{dir}/test/*.rb")
-  # spec.test_objs = Dir.glob("#{dir}/test/*.{c,cpp,m,asm,S}").map { |f| f.relative_path_from(dir).pathmap("#{build_dir}/%X.o") }
-  # spec.test_preload = 'test/assert.rb'
+
+  spec.cc.include_paths << "#{build.root}/src"
 end