Clarify ban evasion policy (llvm#137298)

This documents what the Code of Conduct committee has decided to do when
an attempt to evade a ban is detected.

Author: kbeyls

llvm/docs/DeveloperPolicy.rst

@@ -722,6 +722,8 @@ Indirect contributions are permissible only by someone taking full ownership of
 such a contribution and they are responsible for all related interactions with
 the community regarding that contribution.
 
+Trying to evade a non-permanent ban results in getting banned permanently.
+
 When in doubt how to act in a specific instance, please reach out to
 conduct@llvm.org for advice.