[clang] [NFC] Refactor fast-math handling for clang driver (PR #81173)

[Aaron Ballman via cfe-commits]

================
@@ -2842,9 +2862,8 @@ static void RenderFloatingPointOptions(const ToolChain &TC, const Driver &D,
             << Args.MakeArgString("-ffp-model=" + FPModel)
             << Args.MakeArgString("-ffp-model=" + Val);
       if (Val.equals("fast")) {
-        optID = options::OPT_ffast_math;
         FPModel = Val;
-        FPContract = "fast";
+        applyFastMath();
----------------
AaronBallman wrote:

This seems like it's not an NFC change, right? We used to fail to set a whole pile of flags and now we're setting them correctly?

https://github.com/llvm/llvm-project/pull/81173