77fb0cd3aa
Remove the ThinLTO CU hack This reverts #46722, commit e0ab5d5feb4eb2d8af11b8dd9446c2b45fada8af. Since #111167, commit 10b69dde3fd15334ea2382d2dc9e9a261de1afaf, we are generating DWARF subprograms in a way that is meant to be more compatible with LLVM's expectations, so hopefully we don't need this workaround rewriting CUs anymore.
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.