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

[Shunsuke Watanabe via cfe-commits]

s-watanabe314 wrote:

@andykaylor @AaronBallman What do you think about making the warnings about complex range behave as described above? Any feedback would be greatly appreciated.

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