[llvm] [X86] Add support for indirect branch tracking in jump tables (PR #77679)

[Fangrui Song via llvm-commits]

MaskRay wrote:

It looks like GCC provides `-mcet-switch` to remove NOTRACK in favor or ENDBR in every case handler. It defaults to off, however, as I understand the overwhelming opinion on https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104816 and AArch64 BTI's preference, `-mcet-switch` should default to on and there is actually no point providing the option. In Clang, perhaps we should just always use ENDBR to simplify LTO handling.

https://github.com/llvm/llvm-project/pull/77679