Notifies the codegen to put a static/static mut inside of a specific memory address space.
This is mostly for internal use and/or advanced users, as the codegen and cuda_std handle address space placement
implicitly. Improper use of this macro could yield weird or undefined behavior.
Notifies the codegen that this function is externally visible and should not be
removed if it is not used by a kernel. Usually used for linking with other PTX/cubin files.