We want to automatically copy the appropriate mailing list
for review requests to the libc++abi repository.
For context, see the proposal and discussion here:
Similar to D40500, I set up a new Diffusion repository with callsign
"CXXA" for libc++abi:
This explicitly updates libcxxabi's .arcconfig to point to the new
CXX repository in Diffusion, which will let us use Herald rule H268.