You Need Your CI to Build AMIs with Code Pre-Installed

Multiple Choice

You need your CI to build AMIs with code pre-installed on the images on every new code push. You need to do this as cheaply as possible. How do you do this?

A) Bid on spot instances just above the asking price as soon as new commits come in, perform all instance configuration and setup, then create an AMI based on the spot instance.
B) Have the CI launch a new on-demand EC2 instance when new commits come in, perform all instance configuration and setup, then create an AMI based on the on-demand instance.
C) Purchase a Light Utilization Reserved Instance to save money on the continuous integration machine. Use these credits whenever your create AMIs on instances.
D) When the CI instance receives commits, attach a new EBS volume to the CI machine. Perform all setup on this EBS volume so you do not need a new EC2 instance to create the AMI.