Build time: make hostboot ccache friendly #2996
Description
Complete stewartsmith/hostboot@066cb4b work to ensure Hostboot XML processing, given the same input, produces the same output.
Otherwise you end up defeating ccache and dramatically increasing build times for the cases where the input XML isn't the thing that has changed.
With this patch, rebuilding hostboot as part of op-build goes from
around 16 minutes to less than 3 minutes.