[clang] Add flag to suppress overflow errors in C++ constant expressions. (PR #102390)

[Eli Friedman via cfe-commits]

efriedma-quic wrote:

Note I'm not really attached to merging this either.  I mostly posted this to have a space to discuss the consequences of #70307/#100452.  If the decision is that we don't want this, I'm fine with that.

Also, if we change our mind based on user reports, this would be pretty safe to cherry-pick to a patch release.

https://github.com/llvm/llvm-project/pull/102390