Unfortunately, multiple people are reporting linker warnings related to `__rust_no_alloc_shim_is_unstable` after this change. The solution isn't quite clear yet, let's revert to green for now, and try a reland with a determined solution for `__rust_no_alloc_shim_is_unstable`. This reverts commitc8b7f32434, reversing changes made to667247db71.
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.