[clang] [clang] Suggest using __VA_OPT__(,) instead of GNU zero variadic macro argument (PR #188624)

[via cfe-commits]

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serge-sans-paille wrote:

There are already a lot of tests (102 !) under clang/test/ that don't use the FixIt folder, if you don't mind I don't feel like duplicating the test under two folders for a relatively minor patch.

https://github.com/llvm/llvm-project/pull/188624