[clang] [Clang] Add "extend lifetime" flags and release note (PR #110000)

[Stephen Tozer via cfe-commits]

SLTozer wrote:

> As far as I understand it, these are driver options that will be passed through to cc1? In that case we can at least test the passthrough, i.e. that `-fextend-lifetimes` appears in the output of `-###`.

I think my preferred approach would be to merge both patches simultaneously, or else roll this patch into the next one - we have some tests that use `-###` to test some meaningful logic, but this would essentially be testing that TableGen hasn't bugged out (for this specific flag).


https://github.com/llvm/llvm-project/pull/110000