[clang] [clang][driver] Improve warning message for complex range overrides and GCC incompatibility (PR #149028)

[Zahira Ammarguellat via cfe-commits]

zahiraam wrote:

**IMHO** this is going to be way too complicated, and we should stick to have the last command wins in clang even when incompatibility with GCC occurs. IIRC GCC is not even consistent with the combination of these flags. Adding the `-ffast-math` flag on top of all this, will definitely make things more cumbersome. We can wait for Andy's opinion too. 

https://github.com/llvm/llvm-project/pull/149028