Use gdb on Heroku! Happy debugging!
heroku config:add BUILDPACK_URL=https://github.com/ddollar/heroku-buildpack-multi.git
cat << EOF > .buildpacks
https://github.com/keiko713/heroku-buildpack-gdb.git
https://github.com/heroku/heroku-buildpack-ruby.git
EOF