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

[Florian Hahn via cfe-commits]

fhahn wrote:

> @fhahn we have identified a bunch of tests at google that fail somewhere in the open source library https://code.videolan.org/videolan/x264. The `x264` is built with `-fstrict-aliasing`. All tests pass when removing `-fstrict-aliasing` or disabling Pointer-TBAA (`-fno-pointer-tbaa`).
> 
> Is this expected? Are the two mutually exclusive?

This is likely caused by strict-aliasing violations in the source, could you share a reproducer or steps on how to reproduce?

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