[clang] [Clang] Expand test to include x86_64 and i386 both -O0 and -O2 (PR #191944)

[Nick Desaulniers via cfe-commits]

https://github.com/nickdesaulniers commented:

If this is prepatory work for https://github.com/llvm/llvm-project/pull/181973, please note so in the PR description and commit message.

https://github.com/llvm/llvm-project/pull/191944