15283f6fe9
Extends AArch64 branch protection support to include GCS Extends existing support for AArch64 branch protection to include support for [Guarded Control Stacks](https://community.arm.com/arm-community-blogs/b/architectures-and-processors-blog/posts/arm-a-profile-architecture-2022#guarded-control-stack-gcs:~:text=Extraction%20or%20tracking.-,Guarded%20Control%20Stack%20(GCS),-With%20the%202022).
The codegen crate contains the code to convert from MIR into LLVM IR,
and then from LLVM IR into machine code. In general it contains code
that runs towards the end of the compilation process.
For more information about how codegen works, see the rustc dev guide.