I used this to manually set up my vagrant box once OS X stopped compiling 1.9.2 and I am still stuck with it on my hoster.

vagrant init trusty64 trusty64.box
# now edit your Vagrantfile to include something like
  config.vm.network "forwarded_port", guest: 3000, host: 3696
# to put your rails app wherever you like it
vagrant up
vagrant ssh
sudo apt-get update
sudo apt-get install build-essential zlib1g-dev git-core sqlite3 libsqlite3-dev
sudo apt-get install libssl-dev libqt4-dev libpq-dev libreadline-gplv2-dev xvfb
#trusty should work with QT5 , but it won’t compile capybara-webkit later on
# with sudo apt-get install libpq-dev libssl-dev g++ qt5-default libqt5webkit5-dev
git clone https://github.com/sstephenson/rbenv.git ~/.rbenv
# Ubuntu uses .profile for login-shells, but it will be ignored if a .bash_profile is around, so beware of the orig instructions
echo 'export PATH="$HOME/.rbenv/bin:$PATH"' >> ~/.profile
echo 'eval "$(rbenv init -)"' >> ~/.profile
git clone https://github.com/sstephenson/ruby-build.git ~/.rbenv/plugins/ruby-build
exit
vagrant ssh
rbenv install 1.9.2-p330
cd /vagrant
gem install bundler
rbenv rehash
bundle install
xvfb-run --auto-servernum bundle exec rake test