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

[Andy Kaylor via cfe-commits]

andykaylor wrote:

This is a refreshed version of https://github.com/llvm/llvm-project/pull/91271. Given how long it's been since I updated that PR, it seemed better to just start fresh.

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