Ruby 1.9.3 with SemaphorApp

If you are trying to build a Ruby application using SemaphoreApp and getting errors with 1.9.3 releated to ruby_debug

undefined symbol: ruby_current_thread

The issue is probably that you have the debugger or ruby_debug gem in your Gemfile and it is not building properly on 1.9.3.

You can just add

--without development

to your default bundle install command to avoid building the debugger gem and get your projects to run