[clang] [llvm] [OpenACC] Switch Clang to use the Flang 'appertainment' rules for cla… (PR #135372)

[Erich Keane via llvm-commits]

erichkeane wrote:

We're in agreement on all of the 'standards discussion needed' part, and we've filed bugs for them, so i've removed them.  So now we're down to 3 differences, which I will spawn email threads for between us and the OpenACC chair.

https://github.com/llvm/llvm-project/pull/135372