[clang] Clean up denormal handling with -ffp-model, -ffast-math, etc. (PR #89477)

[Fangrui Song via cfe-commits]

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@@ -75,6 +76,7 @@
 // RUN:   --check-prefix=WARN12 %s
 // RUN: %clang -### -ffast-math -ffp-model=strict -c %s 2>&1 | FileCheck \
 // RUN:   --check-prefix=WARN12 %s
+// WARN12: clang
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MaskRay wrote:

`clang` is unneeded. For diagnostics or -cc1 options, we just avoid check `clang` before `-cc1` since `clang` carries very little weight

https://github.com/llvm/llvm-project/pull/89477