[llvm] [DevPolicy] Add guidance to not submit code or reviews on someone else's (PR #69701)

[David Spickett via llvm-commits]

================
@@ -104,6 +104,12 @@ When submitting patches, please do not add confidentiality or non-disclosure
 notices to the patches themselves.  These notices conflict with the LLVM
 licensing terms and may result in your contribution being excluded.
 
+When being asked by someone to add code (e.g. create a PR), or write review
+comments on their behalf, do suggest that they do it directly themselves. Or
+ask the reasons why they're not doing it themselves. There should be few
+legitimate reasons for them not doing so themselves.
+
----------------
DavidSpickett wrote:

Actually I think I am conflating a few things here. This text does not refer to merging an existing PR, but creating your own PR with someone else's code.

So you can ignore most of that, my apologies.

I still think a clearer statement of steps would be good.

https://github.com/llvm/llvm-project/pull/69701