[lld] Set up .arcconfig to point to new Diffusion LLD repository
We want to automatically copy the appropriate mailing list
for review requests to the LLD repository.
For context, see the proposal and discussion here:
Similar to D40179, I set up a new Diffusion repository with callsign
"LLD" for lld:
This explicitly updates lld's .arcconfig to point to the new C
repository in Diffusion, which will let us use Herald rule H270.
Reviewers: peter.smith, ruiu, rafael, sammccall
Reviewed By: sammccall
Subscribers: dlj, bkramer, sammccall, klimek
Differential Revision: https://reviews.llvm.org/D40495