[clang] [flang] [Flang] RFC: Add support for -w option 1/n (PR #90420)

[Andrzej Warzyński via cfe-commits]

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banach-space wrote:

[nit] Once you have more than one prefix, `CHECK` becomes noise. At least IMHO 😅  (we all know that these are "check" lines). You could use more descriptive prefixes instead, e.g. `CHECK-PORT` -> `PORTABILITY` (it wasn't obvious to me that `PORT` stood for "portability"), `CHECK` -> `DEFAULT`.

https://github.com/llvm/llvm-project/pull/90420