[yocto] Conflicting recipes / How to set SSTATE_DUPWHITELIST?

[Peter Vutov]

Performing pretty much a default build of petalinux 2016.4, Yocto gives
me an error because two recipes are creating the same README file. The
conflict is only in the README file, and the build goes fine if I delete
the file after the first recipe creates it but before the second tries
to replace it (but it is bothersome doing this every time).

Since the conflict is only in a README file, the appropriate fix to me
seems to add it to SSTATE_DUPWHITELIST. How would I do this? I've never
used yocto and couldn't ctrl+f information in the manual on where such
options are set. Would it go in the main *.bb file?

Build log: https://pastebin.com/KrzQvW7d