[clang] [OpenACC] Implement 'if' clause for Compute Constructs (PR #88411)

[Alexey Bataev via cfe-commits]

https://github.com/alexey-bataev commented:

General question. Should there be some support in clang/tools/libclang/CIndex.cpp?

https://github.com/llvm/llvm-project/pull/88411