[yocto] Duplicating a build configuration

[Edward Wingate]

I have configured Yocto to build a jethro distribution that I've been
using for the past 3 years.  I want to duplicate this configuration on
another computer as a backup build machine.  I could just copy over
the poky directory and all my layers, but I think this would copy over
unnecessary files (build/tmp, old build artifacts?).

What would be the best way to make this backup computer be capable of
generating the same distribution?  Some of my layers are on the jethro
branch, and others on the master branch. Should I just configure from
scratch (git clone all the layers, set all the right branches)?  Or is
there a better way?  Could/should I reuse the download mirror or the
sstate cache on the original machine?

Thanks for your help/suggestions.

Ed