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

[Andy Kaylor via cfe-commits]

================
@@ -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
----------------
andykaylor wrote:

The only purpose of the check here is to establish a reference point for the WARN12-NOT check on the following line. I can change the thing I'm checking to "-cc1" if that will cause less confusion for people reading the test.

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