Ruby 1.8.7's FileUtils.chmod does not like strings

.travis.yml

@@ -15,7 +15,7 @@ matrix:
     - rvm: 1.8.7
 bundler_args: -j4
 script:
-  - bundle exec rake spec build binary
+  - bundle exec rake spec build binary --trace
   - travis_wait gem install pkg/*.gem
 notifications:
   recipients:

Rakefile

@@ -37,7 +37,7 @@ task :binary => :compile do
   gemspec.files += Dir['vendor/v8/include/*']
   gemspec.files += Dir['vendor/v8/out/**/*.a']
 
-  FileUtils.chmod 'a+r', gemspec.files
+  FileUtils.chmod 0644, gemspec.files
   FileUtils.mkdir_p 'pkg'
 
   package = if Gem::VERSION < '2.0.0'