Specify plaform: :mri for byebug

Author: ianks

railties/lib/rails/generators/rails/app/templates/Gemfile

@@ -26,7 +26,7 @@ source 'https://rubygems.org'
 <% if RUBY_ENGINE == 'ruby' -%>
 group :development, :test do
   # Call 'byebug' anywhere in the code to stop execution and get a debugger console
-  gem 'byebug'
+  gem 'byebug', platform: :mri
 end
 
 group :development do