[clang] [Driver] Clean up fp-contract handling in clang driver (PR #99723)

[Fangrui Song via cfe-commits]

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@@ -10,18 +10,18 @@
 // RUN: %clang -### -fno-fast-math -c %s 2>&1 \
 // RUN:   | FileCheck --check-prefix=CHECK-FPC-ON %s
 
-// RUN: %clang -### -Werror -ffast-math -ffp-contract=on -c %s 2>&1 \
+// RUN: %clang -### -ffast-math -ffp-contract=on -c %s 2>&1 \
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MaskRay wrote:

If these RUN lines now emit warnings (upgraded to errors if -Werror), consider adding check prefixes for the warnings.

https://github.com/llvm/llvm-project/pull/99723