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