d76cff3f06
Don't export them from cdylibs. There is no need to do so and it complicates exported_non_generic_symbols. In addition the GCC backend likely uses different symbols and may potentially not even need us to explicitly tell it to export the symbols it needs.
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.