[clang] [Clang][Driver] Override complex number calculation method by -fno-fast-math (PR #132680)

[Fangrui Song via cfe-commits]

MaskRay wrote:

> Thank you for confirming.
> 
> @MaskRay, do you have any comments regarding the handling of warning messages?

Sorry for the delayed response.  Does this implement the last-option-win behavior as suggested in the last few comments of https://discourse.llvm.org/t/the-priority-of-fno-fast-math-regarding-complex-number-calculations/84679 ? If so, this looks good me.

Another possible behavior is the 'more-specific-option-wins' approach adopted by some options. I am not familiar with the complex number options and don't have a strong opinion. Go with the suggestion by experts like andykaylor!

https://github.com/llvm/llvm-project/pull/132680