Enabling AARCH64 BTI

[William Roberts]

I was looking at packages that don't declare BTI in the GNU Notes
section of the ELF file, and found libffi was missing that.
Investigating libffi, it enables BTI, but does not add it to the notes
section and if it's not in the notes section the linker/loader will
disable BTI for the target process.

https://github.com/libffi/libffi/pull/822

Here are some helpful notes and details on it as explained by others:
  - https://maskray.me/blog/2023-03-05-linker-notes-on-aarch64
  - https://reviews.llvm.org/D62609

Thanks,
Bill