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

[Erich Keane via llvm-commits]

erichkeane wrote:

atomic-if merged, which leaves us at:
```
Failed Tests (6):
  Clang :: SemaOpenACC/combined-construct-auto_seq_independent-clauses.c
  Clang :: SemaOpenACC/compute-construct-num_gangs-clause.c
  Clang :: SemaOpenACC/init-construct.cpp
  Clang :: SemaOpenACC/loop-construct-auto_seq_independent-clauses.c
  Clang :: SemaOpenACC/routine-construct-clauses.cpp
  Clang :: SemaOpenACC/shutdown-construct.cpp
```

Same categorization as above.

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