[clang] [clang][cmake] Don't pass -fno-strict-aliasing for GCC (PR #144222)

[Sam James via cfe-commits]

thesamesam wrote:

FWIW, there seems to be similar code in Flang which was likely copied from Clang, but I'm not in a position to test removing that right now.

https://github.com/llvm/llvm-project/pull/144222