[clang] [clang-tools-extra] [llvm] [clang] Introduce diagnostics suppression mappings (PR #112517)

[kadir çetinkaya via cfe-commits]

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kadircet wrote:

sorry i am struggling to see the value in an integration test while we can (and do) test it in a unittest. can you elaborate ?

https://github.com/llvm/llvm-project/pull/112517