[clang] [Clang] Enable -fpointer-tbaa by default. (PR #117244)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

What are the chances that this will exploit undefined behavior in existing user code in ways that will make upgrading to the latest Clang more difficult because of the perception of "miscompiles?" If this is a likely scenario for users to hit, do other tools like UBSan (etc) help users to find and fix the issues?

I'm not opposed to the changes, I just want to make sure we are setting users up for success when they upgrade.

https://github.com/llvm/llvm-project/pull/117244